diff --git a/README.md b/README.md
index d4e5538..3340ebe 100644
--- a/README.md
+++ b/README.md
@@ -65,6 +65,7 @@ target and a C device driver (unless you can acquire a suitable binary).
 
 # Project status
 
+Sept 2024: Dropdown and Listbox support dynamically variable lists of elements.  
 April 2024: Add screen replace feature for non-tree navigation.  
 Sept 2023: Add "encoder only" mode suggested by @eudoxos.  
 April 2023: Add limited ePaper support, grid widget, calendar and epaper demos.
@@ -128,7 +129,9 @@ under development so check for updates.
  6.5 [ButtonList object](./README.md#65-buttonlist-object) Pushbuttons with multiple states.  
  6.6 [RadioButtons object](./README.md#66-radiobuttons-object) One-of-N pushbuttons.  
  6.7 [Listbox widget](./README.md#67-listbox-widget)  
+      6.7.1 [Dynamic changes](./README.md#671-dynamic-changes) Alter listbox contents at runtime.  
  6.8 [Dropdown widget](./README.md#68-dropdown-widget) Dropdown lists.  
+      6.8.1 [Dynamic changes](./README.md#681-dynamic-changes) Alter dropdown contents at runtime.  
  6.9 [DialogBox class](./README.md#69-dialogbox-class) Pop-up modal dialog boxes.  
  6.10 [Textbox widget](./README.md#610-textbox-widget) Scrolling text display.  
  6.11 [Meter widget](./README.md#611-meter-widget) Display floats on an analog meter, with data driven callbacks.  
@@ -684,6 +687,8 @@ Some of these require larger screens. Required sizes are specified as
  (240x320).
  * `vtest.py` Clock and compass styles of vector display (240x320).
  * `calendar.py` Demo of grid control (240x320 - but could be reduced).
+ * `listbox_var.py` Listbox with dynamically variable elements.
+ * `dropdown_var.py` Dropdown with dynamically variable elements.
 
 ###### [Contents](./README.md#0-contents)
 
@@ -1628,6 +1633,7 @@ Methods:
  the control's list, that item becomes current. Normally returns the current
  string. If a provided arg did not match any list item, the control's state is
  not changed and `None` is returned.
+ * `update` No args. See [Dynamic changes](./README.md#671-dynamic-changes).
 
 The callback's first argument is the listbox instance followed by any args
 specified to the constructor. The currently selected item may be retrieved by
@@ -1668,6 +1674,12 @@ class BaseScreen(Screen):
 
 Screen.change(BaseScreen)
 ```
+### 6.7.1 Dynamic changes
+
+The contents of a listbox may be changed at runtime. To achieve this, elements
+must be defined as a list rather than a tuple. After the application has
+modified the list, it should call the `.update` method to refresh the control.
+The demo script `listbox_var.py` illustrates this.
 
 ###### [Contents](./README.md#0-contents)
 
@@ -1734,6 +1746,7 @@ Methods:
  the control's list, that item becomes current. Normally returns the current
  string. If a provided arg did not match any list item, the control's state is
  not changed and `None` is returned.
+ * `update` No args. See [Dynamic changes](./README.md#681-dynamic-changes).
 
 If `select` is pressed when the `Dropdown` has focus, the list is displayed.
 The `increase` and `decrease` buttons move the list currency. If `select` is
@@ -1784,6 +1797,13 @@ class BaseScreen(Screen):
 
 Screen.change(BaseScreen)
 ```
+### 6.8.1 Dynamic changes
+
+The contents of a Dropdown may be changed at runtime. To achieve this, elements
+must be defined as a list rather than a tuple. After the application has
+modified the list, it should call the `.update` method to refresh the control.
+The demo script `dropdown_var.py` illustrates this.
+
 ###### [Contents](./README.md#0-contents)
 
 ## 6.9 DialogBox class
diff --git a/gui/demos/dropdown_var.py b/gui/demos/dropdown_var.py
new file mode 100644
index 0000000..b430df5
--- /dev/null
+++ b/gui/demos/dropdown_var.py
@@ -0,0 +1,79 @@
+# dropdown_var.py micro-gui demo of Dropdown widget with changeable elements
+
+# Released under the MIT License (MIT). See LICENSE.
+# Copyright (c) 2024 Peter Hinch
+
+# hardware_setup must be imported before other modules because of RAM use.
+import hardware_setup  # Create a display instance
+from gui.core.ugui import Screen, Window, ssd
+
+from gui.widgets import Label, Button, CloseButton, Dropdown
+from gui.core.writer import CWriter
+
+# Font for CWriter
+import gui.fonts.font10 as font
+from gui.core.colors import *
+
+
+def newtext():  # Create new listbox entries
+    strings = ("Iron", "Copper", "Lead", "Zinc")
+    n = 0
+    while True:
+        yield strings[n]
+        n = (n + 1) % len(strings)
+
+
+ntxt = newtext()  # Instantiate the generator
+
+
+class BaseScreen(Screen):
+    def __init__(self):
+
+        super().__init__()
+        wri = CWriter(ssd, font, GREEN, BLACK, verbose=False)
+
+        col = 2
+        row = 2
+        self.els = ["Hydrogen", "Helium", "Neon", "Argon", "Krypton", "Xenon", "Radon"]
+        self.dd = Dropdown(
+            wri,
+            row,
+            col,
+            elements=self.els,
+            dlines=5,  # Show 5 lines
+            bdcolor=GREEN,
+            callback=self.ddcb,
+        )
+        row += 30
+        self.lbl = Label(wri, row, col, self.dd.width, bdcolor=RED)
+        b = Button(wri, 2, 120, text="del", callback=self.delcb)
+        b = Button(wri, b.mrow + 2, 120, text="add", callback=self.addcb)
+        b = Button(wri, b.mrow + 10, 120, text="h2", callback=self.gocb, args=("Hydrogen",))
+        b = Button(wri, b.mrow + 2, 120, text="fe", callback=self.gocb, args=("Iron",))
+        CloseButton(wri)
+
+    def gocb(self, _, txt):  # Go button callback: Move currency to specified entry
+        self.dd.textvalue(txt)
+
+    def addcb(self, _):  # Add button callback
+        self.els.append(next(ntxt))  # Append a new entry
+        self.dd.update()
+
+    def delcb(self, _):  # Delete button callback
+        del self.els[self.dd.value()]  # Delete current entry
+        self.dd.update()
+
+    def ddcb(self, dd):
+        if hasattr(self, "lbl"):
+            self.lbl.value(dd.textvalue())
+
+    def after_open(self):
+        self.lbl.value(self.dd.textvalue())
+
+
+def test():
+    print("Dropdown demo.")
+    Screen.change(BaseScreen)
+
+
+test()
diff --git a/gui/demos/listbox_var.py b/gui/demos/listbox_var.py
new file mode 100644
index 0000000..c29a05a
--- /dev/null
+++ b/gui/demos/listbox_var.py
@@ -0,0 +1,74 @@
+# listbox_var.py micro-gui demo of Listbox class with variable elements
+
+# Released under the MIT License (MIT). See LICENSE.
+# Copyright (c) 2024 Peter Hinch
+
+# hardware_setup must be imported before other modules because of RAM use.
+from hardware_setup import ssd  # Create a display instance
+from gui.core.ugui import Screen
+from gui.core.writer import CWriter
+from gui.core.colors import *
+
+from gui.widgets import Listbox, Button, CloseButton
+import gui.fonts.freesans20 as font
+
+
+def newtext():  # Create new listbox entries
+    strings = ("Iron", "Copper", "Lead", "Zinc")
+    n = 0
+    while True:
+        yield strings[n]
+        n = (n + 1) % len(strings)
+
+
+ntxt = newtext()  # Instantiate the generator
+
+
+class BaseScreen(Screen):
+    def __init__(self):
+
+        super().__init__()
+        wri = CWriter(ssd, font, GREEN, BLACK, verbose=False)
+        self.els = [
+            "Hydrogen",
+            "Helium",
+            "Neon",
+            "Xenon",
+            "Radon",
+            "Uranium",
+            "Plutonium",
+            "Actinium",
+        ]
+        self.lb = Listbox(
+            wri,
+            2,
+            2,
+            elements=self.els,
+            dlines=5,
+            bdcolor=RED,
+            value=1,
+            callback=self.lbcb,
+            also=Listbox.ON_LEAVE,
+        )
+        Button(wri, 2, 120, height=25, text="del", callback=self.delcb)
+        Button(wri, 32, 120, height=25, text="add", callback=self.addcb)
+        Button(wri, 62, 120, height=25, text="h2", callback=self.gocb, args=("Hydrogen",))
+        Button(wri, 92, 120, height=25, text="fe", callback=self.gocb, args=("Iron",))
+        CloseButton(wri)
+
+    def lbcb(self, lb):  # Listbox callback
+        print(lb.textvalue())
+
+    def gocb(self, _, txt):  # Go button callback: Move currency to specified entry
+        self.lb.textvalue(txt)
+
+    def addcb(self, _):  # Add button callback
+        self.els.append(next(ntxt))  # Append a new entry
+        self.lb.update()
+
+    def delcb(self, _):  # Delete button callback
+        del self.els[self.lb.value()]  # Delete current entry
+        self.lb.update()
+
+
+Screen.change(BaseScreen)
diff --git a/gui/widgets/dropdown.py b/gui/widgets/dropdown.py
index 5a9a216..a9722d3 100644
--- a/gui/widgets/dropdown.py
+++ b/gui/widgets/dropdown.py
@@ -10,12 +10,11 @@ from gui.core.colors import *
 
 from gui.widgets.listbox import Listbox
 
-dolittle = lambda *_ : None
+dolittle = lambda *_: None
 
 # Next and Prev close the listbox without updating the Dropdown. This is
 # handled by Screen .move bound method
 class _ListDialog(Window):
-
     def __init__(self, writer, row, col, dd):  # dd is parent dropdown
         # Need to determine Window dimensions from size of Listbox, which
         # depends on number and length of elements.
@@ -25,63 +24,89 @@ class _ListDialog(Window):
         ap_height = lb_height + 6  # Allow for listbox border
         ap_width = lb_width + 6
         super().__init__(row, col, ap_height, ap_width, draw_border=False)
-        self.listbox = Listbox(writer, row + 3, col + 3,
-                               elements = dd.elements,
-                               dlines = dlines, width = lb_width,
-                               fgcolor = dd.fgcolor, bgcolor = dd.bgcolor,
-                               bdcolor=False, fontcolor = dd.fontcolor,
-                               select_color = dd.select_color,
-                               value = dd.value(), callback = self.callback)
+        self.listbox = Listbox(
+            writer,
+            row + 3,
+            col + 3,
+            elements=dd.elements,
+            dlines=dlines,
+            width=lb_width,
+            fgcolor=dd.fgcolor,
+            bgcolor=dd.bgcolor,
+            bdcolor=False,
+            fontcolor=dd.fontcolor,
+            select_color=dd.select_color,
+            value=dd.value(),
+            callback=self.callback,
+        )
         self.dd = dd
 
     def callback(self, obj_listbox):
         display.ipdev.adj_mode(False)  # If in 3-button mode, leave adjust mode
         Screen.back()
-        self.dd.value(obj_listbox.value()) # Update it
+        self.dd.value(obj_listbox.value())  # Update it
 
 
 class Dropdown(Widget):
-    def __init__(self, writer, row, col, *,
-                 elements,
-                 dlines=None, width=None, value=0,
-                 fgcolor=None, bgcolor=None, bdcolor=False,
-                 fontcolor=None, select_color=DARKBLUE,
-                 callback=dolittle, args=[]):
+    def __init__(
+        self,
+        writer,
+        row,
+        col,
+        *,
+        elements,
+        dlines=None,
+        width=None,
+        value=0,
+        fgcolor=None,
+        bgcolor=None,
+        bdcolor=False,
+        fontcolor=None,
+        select_color=DARKBLUE,
+        callback=dolittle,
+        args=[],
+    ):
 
-        self.entry_height = writer.height + 2 # Allow a pixel above and below text
+        self.entry_height = writer.height + 2  # Allow a pixel above and below text
         height = self.entry_height
-        e0 = elements[0]
+        self.select_color = select_color
+        self.dlines = dlines  # Referenced by _ListDialog
+
         # Check whether elements specified as (str, str,...) or ([str, callback, args], [...)
-        if isinstance(e0, tuple) or isinstance(e0, list):
-            te = [x[0] for x in elements]  # Copy text component
-            self.els = elements  # Retain original
-            elements = te
-            if callback is not dolittle:
-                raise ValueError('Cannot specify callback.')
-            callback = self._despatch
+        self.simple = isinstance(elements[0], str)
+        self.els = elements  # Retain original
+        # Listbox works with text component only because it has a single callback.
+        self.elements = elements if self.simple else [x[0] for x in elements]
         if width is None:  # Allow for square at end for arrow
             self.textwidth = max(writer.stringlen(s) for s in elements)
             width = self.textwidth + 2 + height
         else:
             self.textwidth = width
         super().__init__(writer, row, col, height, width, fgcolor, bgcolor, bdcolor, value, True)
-        super()._set_callbacks(callback, args)
-        self.select_color = select_color
         self.fontcolor = self.fgcolor if fontcolor is None else fontcolor
-        self.elements = elements
-        self.dlines = dlines
+        if not self.simple:
+            if callback is not dolittle:
+                raise ValueError("Cannot specify callback.")
+            callback = self._despatch  # Override passed CB if each element has a CB.
+        super()._set_callbacks(callback, args)  # Callback runs on value change
+
+    def update(self):  # Elements list has changed. Extract text component for dropdown.
+        self.elements = self.els if self.simple else [x[0] for x in self.els]
+        # Ensure sensible _value if list size is reduced.
+        self._value = min(self._value, len(self.els) - 1)
+        self.show()
 
     def show(self):
-        if super().show():
-            x, y = self.col, self.row
-            self._draw(x, y)
-            if self._value is not None:
-                display.print_left(self.writer, x, y + 1, self.elements[self._value], self.fontcolor)
+        if not super().show():
+            return
+        self._draw(x := self.col, y := self.row)
+        if self._value is not None:
+            display.print_left(self.writer, x, y + 1, self.elements[self._value], self.fontcolor)
 
-    def textvalue(self, text=None): # if no arg return current text
+    def textvalue(self, text=None):  # if no arg return current text
         if text is None:
             return self.elements[self._value]
-        else: # set value by text
+        else:  # set value by text
             try:
                 v = self.elements.index(text)
             except ValueError:
@@ -92,21 +117,33 @@ class Dropdown(Widget):
             return v
 
     def _draw(self, x, y):
-        #self.draw_border()
+        # self.draw_border()
         display.vline(x + self.width - self.height, y, self.height, self.fgcolor)
-        xcentre = x + self.width - self.height // 2 # Centre of triangle
+        xcentre = x + self.width - self.height // 2  # Centre of triangle
         ycentre = y + self.height // 2
         halflength = (self.height - 8) // 2
         length = halflength * 2
         if length > 0:
             display.hline(xcentre - halflength, ycentre - halflength, length, self.fgcolor)
-            display.line(xcentre - halflength, ycentre - halflength, xcentre, ycentre + halflength, self.fgcolor)
-            display.line(xcentre + halflength, ycentre - halflength, xcentre, ycentre + halflength, self.fgcolor)
+            display.line(
+                xcentre - halflength,
+                ycentre - halflength,
+                xcentre,
+                ycentre + halflength,
+                self.fgcolor,
+            )
+            display.line(
+                xcentre + halflength,
+                ycentre - halflength,
+                xcentre,
+                ycentre + halflength,
+                self.fgcolor,
+            )
 
     def do_sel(self):  # Select was pushed
         if len(self.elements) > 1:
             args = (self.writer, self.row - 2, self.col - 2, self)
-            Screen.change(_ListDialog, args = args)
+            Screen.change(_ListDialog, args=args)
             display.ipdev.adj_mode(True)  # If in 3-button mode, go into adjust mode
 
     def _despatch(self, _):  # Run the callback specified in elements
diff --git a/gui/widgets/listbox.py b/gui/widgets/listbox.py
index ae83b27..41171a3 100644
--- a/gui/widgets/listbox.py
+++ b/gui/widgets/listbox.py
@@ -29,7 +29,9 @@ class Listbox(Widget):
         dlines = len(elements) if dlines is None else dlines
         # Height of control
         height = entry_height * dlines + 2
-        textwidth = max(writer.stringlen(s) for s in elements) + 4
+        simple = isinstance(elements[0], str)  # list or list of lists?
+        q = (p for p in elements) if simple else (p[0] for p in elements)
+        textwidth = max(writer.stringlen(x) for x in q) + 4
         return entry_height, height, dlines, textwidth
 
     def __init__(
@@ -52,25 +54,23 @@ class Listbox(Widget):
         also=0
     ):
 
-        e0 = elements[0]
+        self.els = elements
         # Check whether elements specified as (str, str,...) or ([str, callback, args], [...)
-        if isinstance(e0, tuple) or isinstance(e0, list):
-            self.els = elements  # Retain original for .despatch
-            self.elements = [x[0] for x in elements]  # Copy text component
-            if callback is not dolittle:
-                raise ValueError("Cannot specify callback.")
-            self.cb = self.despatch
-        else:
-            self.cb = callback
-            self.elements = elements
-        if any(not isinstance(s, str) for s in self.elements):
+        self.simple = isinstance(self.els[0], str)
+        self.cb = callback if self.simple else self.despatch
+        if not self.simple and callback is not dolittle:
+            raise ValueError("Cannot specify callback.")
+        # Iterate text values
+        q = (p for p in self.els) if self.simple else (p[0] for p in self.els)
+        if not all(isinstance(x, str) for x in q):
             raise ValueError("Invalid elements arg.")
+
         # Calculate dimensions
-        self.entry_height, height, self.dlines, tw = self.dimensions(writer, self.elements, dlines)
+        self.entry_height, height, self.dlines, tw = self.dimensions(writer, self.els, dlines)
         if width is None:
             width = tw  # Text width
 
-        self.also = also
+        self.also = also  # Additioal callback events
         self.ntop = 0  # Top visible line
         if not isinstance(value, int):
             value = 0  # Or ValueError?
@@ -86,7 +86,7 @@ class Listbox(Widget):
         self.ev = value  # Value change detection
 
     def update(self):  # Elements list has changed.
-        l = len(self.elements)
+        l = len(self.els)
         nl = self.dlines  # No. of lines that can fit in window
         self.ntop = max(0, min(self.ntop, l - nl))
         self._value = min(self._value, l - 1)
@@ -99,11 +99,13 @@ class Listbox(Widget):
         x = self.col
         y = self.row
         eh = self.entry_height
-        ntop = self.ntop
         dlines = self.dlines
-        nlines = min(dlines, len(self.elements))  # Displayable lines
+        self.ntop = min(self.ntop, self._value)  # Ensure currency is visible
+        self.ntop = max(self.ntop, self._value - dlines + 1)
+        ntop = self.ntop
+        nlines = min(dlines, len(self.els))  # Displayable lines
         for n in range(ntop, ntop + nlines):
-            text = self.elements[n]
+            text = self.els[n] if self.simple else self.els[n][0]
             if self.writer.stringlen(text) > self.width:  # Clip
                 font = self.writer.font
                 pos = 0
@@ -126,18 +128,25 @@ class Listbox(Widget):
         x = self.col + self.width - 2
         if ntop:
             display.vline(x, self.row, eh - 1, self.fgcolor)
-        if ntop + dlines < len(self.elements):
+        if ntop + dlines < len(self.els):
             y = self.row + (dlines - 1) * eh
             display.vline(x, y, eh - 1, self.fgcolor)
 
     def textvalue(self, text=None):  # if no arg return current text
         if text is None:
-            return self.elements[self._value]
+            r = self.els[self._value]
+            return r if self.simple else r[0]
         else:  # set value by text
             try:
                 # print(text)
-                # print(self.elements.index(text))
-                v = self.elements.index(text)
+                # print(self.els.index(text))
+                if self.simple:
+                    v = self.els.index(text)
+                else:  # More RAM-efficient than converting to list and using .index
+                    q = (p[0] for p in self.els)
+                    v = 0
+                    while next(q) != text:
+                        v += 1
             except ValueError:
                 v = None
             else:
@@ -161,7 +170,7 @@ class Listbox(Widget):
             if v:
                 self._vchange(v - 1)
         elif val < 0:
-            if v < len(self.elements) - 1:
+            if v < len(self.els) - 1:
                 self._vchange(v + 1)
 
     # Callback runs if select is pressed. Also (if ON_LEAVE) if user changes