Eighty patients with 'primary' dural sinus and cerebral venous thrombosis were seen over a period of 16 years. There was an equal distribution amongst the sexes and the largest number of patients presented in the third decade. The commonest predisposing factors were puerperium, pregnancy, synthetic steroid contraceptives and anaemia. Seventy patients presented in an acute fashion with headache, focal or generalized seizures and focal neurological deficits. Ten patients presented in a subacute to chronic manner, with features to suggest an intracerebral space-occupying lesion. The investigation of choice was angiography. Thirty-five patients were treated conservatively with anticonvulsants, low molecular weight dextran and anti-oedema measures. Anti-coagulants were not used for fear of haemorrhage in the associated red infarcts. Antibiotics were not needed as infection played no part in the pathogenesis. Thirty-four patients needed an operation which took the form of a decompressive craniotomy and dural closure with the aid of a pericranial graft. The conservatively treated group appeared to fare better only because it included patients with a milder ictus. Forty patients improved, three remained unchanged and 37 expired. Autopsy in the 35 of the 37 patients showed cortical vein and sinus thrombosis and oedema with a haemorrhagic infarct. Long term follow-up showed good recovery of neurological function, but epilepsy was a troublesome sequel and needs regular anti-epileptic drug treatment.