Sorry to dig up this post but after trying to using a cpp class from an dll (http://www.delphi3000.com/articles/article_2708.asp?SK=) i though by myselves hey this must also be possible with delphi class in an dll. I could not get it to work at first but searching on the forum here i found this thread. The solve seems to be creating a base class that is used as an interface. And inherit the class in the dll from that one. Why is this needed, i do not need it for the cpp one, so why is this needed for the delphi class. I can live with it though, but i am curious for the why and can it be done without like the cpp class to delphi.