Userform Option (Radial) Button - Retain Last choice

You could store the result in a Named Constant (similar to a Named Range).

Private Sub OptionButton1_Click()
    Application.Names.Add "ufGender", "Male", False
End Sub

Private Sub OptionButton2_Click()
    Application.Names.Add "ufGender", "Female", False
End Sub


Private Sub UserForm_Initialize()
    If Not IsError(Evaluate("ufGender")) Then
        Select Case Evaluate("ufGender")
           Case "Male": OptionButton1.Value = True
           Case "Female": OptionButton2.Value = True
        End Select
    End If
End Sub

On a side note:
I think they are colloquially referred to as Radio buttons and not Radial because they mimic the radio station push buttons on old-style radios with mechanical tuners. The radio station preset buttons would be pushed in and stay pushed in until a different preset station button was pushed. I could be very wrong on this.

You're welcome.

Originally Posted by vba_madness

Is the constant stored when the document is closed?

Yes, if the workbook is saved

Apart from via VBA and the Immediate Window, is there somewhere that I can see this (and potentially other Named Constants) is/are stored?

You can see them in the Name manager if you make this argument TRUE
Application.Names.Add "ufGender", "Male", True

Any warnings/caveats/restrictions that should be borne in mind when using a Named Constant?

None that I can think of other than saving the workbook.

Is there any other way that you might go about this?

You could write the value to a text file or store the value in the user's registry.