Build your test application. Then go back to your DLL project. Go to the Run menu. Select the Parameters menu item. In the Host Application area, put the path to your test application .exe. NOTE: I'm telling you this from D5. I don't have D6 installed, but I think it was the same process. Another issue you may run into (D5 suffers from this is), the breakpoints will disappear. This is a well known bug in D5 and debugging DLLs. Should this happen, make your test application test your DLL by using buttons. This way here, it won't automatically run through the DLL code. Before hitting a button (or some other control), go to the IDE. Go to the View->Debug Windows->Modules (or Ctrl+Alt+M). Right click your DLL in the list. Select Reload Symbol Table. This enter that path of your DLL. You should see your breakpoints re-appear. Hope you find this information useful.