I'm trying to learn QT4. But it seems as i can't compile any program... I'm following this very basic guide: http://doc.trolltech.com/4.0/tutorial-t1.html But when i try to compile it i get: Code: emil@MacBooken.local: ~/Desktop $ g++ QT-hello.cpp QT-hello.cpp:1:24: error: QApplication: No such file or directory QT-hello.cpp:2:23: error: QPushButton: No such file or directory QT-hello.cpp: In function 'int main(int, char**)': QT-hello.cpp:6: error: 'QApplication' was not declared in this scope QT-hello.cpp:6: error: expected `;' before 'app' QT-hello.cpp:8: error: 'QPushButton' was not declared in this scope QT-hello.cpp:8: error: expected `;' before 'hello' QT-hello.cpp:9: error: 'hello' was not declared in this scope QT-hello.cpp:12: error: 'app' was not declared in this scope I know i got these errors in GNU/Linux when i tried to compile some programs some time ago, but the errors where gone after i installed some dev-libs. Now, in OS X i have installed "qt-mac-opensource-4.3.2.dmg" from: http://trolltech.com/developer/downloads/qt/mac But i still get these errors! How do i get rid off them?