The creep behaviour and dislocation structure of polycrystalline Ni3Al have been investigated at intermediate temperatures, where macroscopic inverse creep may or may not be present depending upon both the temperature and the stress applied. Microstructural observations indicate that superdislocations slip on the cube cross-slip plane more easily at lower temperatures, and is one of the reasons causing the creep strength to vary anomalously with temperature. Although inverse creep is produced by the operation of cube cross-slip, it is a necessary but not sufficient condition, i.e. the operation of cube cross-slip may not necessarily result in macroscopic inverse creep.