To reproduce: handle the following event and start typing in the editable part. You will notice that the TextChanged event is not fired: Me.RadPopupEditor1.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDown AddHandler Me.RadPopupEditor1.TextChanged, AddressOf RadPopupEditor1_TextChanged Workaround: handle the RadPopupEditor.TextBoxElement.TextChanged event instead.