Medical notes of 123 patients with subarachnoid haemorrhage were examined. No patient deteriorated at the time of lumbar puncture. All but 2 patients with associated intracerebral haematomas had markedly impaired consciousness or focal signs. Two of 30 patients with meningitis were initially diagnosed as subarachnoid haemorrhage, and one died without lumbar puncture. If consciousness is not markedly impaired and focal signs are absent, lumbar puncture is safe in patients with subarachnoid haemorrhage.