Yes, one should ALWAYS subclass PaletteSet, just as we do with System.Windows.Forms.Form: we always derive our form from Form, as long as you use AutoCAD 2009 or later (prior to Acad2009, PaletteSet is a sealed class, which cannot be subclassed). I saw your post earlier in Autodesk's .NET forum, referring to an old AU class material, which gave pretty good sample code of PaletteSet. But since it was for pre Acad2009, thus did not subclass PaletteSet, thus should be considered very out-of-date.