Prior to Qt 4.8, ActiveQt was built when using MinGW. Now it seems to be disabled: https://qt.gitorious.org/qt/qt/merge_requests/1336. Please revert this merge so ActiveQt is enabled again. There is no problem building ActiveQt with MinGW. I have tested with MinGW GCC 4.4.0 (included with Qt SDK and Qt Creator) and MinGW-w64 GCC 4.5.2 TDM64-1.