In a retrospective survey of 66 cases (46 proven) of cerebral venous thrombosis in a large number of public teaching hospitals in Australia, the quantity of cases in institutions of similar size varied widely. There were 29 fatal cases (all underwent an autopsy) and in 20 of these the venous thrombosis was considered to be the major cause of death. In 15 of the deaths due to cerebral venous thrombosis the diagnosis was not suspected before death. In 27 cases (18 proven) the underlying cause was infection, while only two cases (both confirmed) were associated with oral contraceptives. These findings suggest that although rare, cerebral venous thrombosis is underdiagnosed and that, even in the era of modern antibiotics, sepsis is the commonest single identifiable cause.