Hi If I create a new (Form) class using Visual Studio and then subclass it in Python then I get "TypeError: no method matches given arguments" when executing 'WinForms.Application.Run(self)'. The new Form instance is created OK and the following returns true: 'isinstance(form, System.Windows.Forms.Form)' The only differences from the working examples appear to be: 1. The parameter is an object subclassed from a class that is in turn subclassed from System.Windows.Forms.Form. (The intermediate class is written in C#). 2. The class I created is not in the GAC. It is loaded using 'Assembly.LoadFile("D:\\forecastdev\\net\\TestGraphs\\bin\\Debug\\TestGraphs .exe")' Has anybody any suggestions? Regards Gordon --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.532 / Virus Database: 326 - Release Date: 27/10/2003