Trying something new...I added the [assembly: CommandClass()] entries for all commands, including those in the second project, into one class in the main project. At load time in Autocad I got an eDuplicateKey error. I went back and commented out the 3 lines that point to those in the second project, then it loaded without error. But then, of course, those commands didn't work. So I added just those 3 lines into the AssemblyInfo for the second project, everything still loads fine, but those commands in the second project still no worky. It looks like I need to keep all of the CommandMethods in the main project and just call the methods in the second project. Not ideal, and it's only 7 commands, but it makes me wonder what others do in a Solution with many others working in different projects. It looked like the link JeffH gave might go into that, but I think it fell short of describing what to do...or maybe I missed it.