 <p>If you are trying to restrict the maximum size of the form when the user tries to maximise it then this will work. I have my own Form class descended from <code>TForm</code> called <code>TRGNewForm</code> and all my forms descend from that. However the scheme will work for the form you put the code in.</p> <p>In the <code>Interface</code> section, in your Form class Public definition </p> <pre><code> { Trap Sys Commands } procedure WMSysCommand (var Msg: TWMSysCommand); message WM_SYSCOMMAND; </code></pre> <p>In the <code>Implementation</code> </p> <pre><code>procedure TRGNewForm.WMSysCommand (var Msg : TWMSysCommand); begin { If MdiChild and Maximize button pressed, then use our own routine, as Windows has a bug } if (Msg.CmdType = SC_MAXIMIZE) and (FormStyle = fsMDIChild) then Maximise_Child_Form else DefaultHandler (Msg); end; </code></pre> <p>In <code>Maximise_Child_Form</code> you set the height and width as required. </p>