The results of a 4-year prospective study of stroke in a community of 140,000 people are reported. Eight hundred and forty-two strokes were recorded, 70 per cent in University Hospitals, 20 per cent in private hospitals and 10 per cent at home. Ninety-four per cent of the patients had a CT scan. The annual incidence of stroke was 145/100,000 people, whereas the incidences of infarct, cerebral haemorrhage and subarachnoid haemorrhage were 121, 21 and 6.6/100,000 people respectively. These results, compared with those of other registers, clearly show the superiority of population-based registers over hospital-based registers.