Four cases are presented, in whom cerebellar haemorrhages appeared as a complication following supratentorial craniotomy for a giant aneurysm, for tumours in three cases. Two patients died. Intracranial hypotension in combination with disturbed blood coagulation is discussed as possible pathogenesis. Because this seems to be a rare complication--similar cases have not yet been described in the literature--its timely diagnosis may be missed.