The SEPIVAC study is a community-based epidemiological survey of incidence and outcome of acute cerebrovascular disease in the Sixth Local Health Unit, Umbria, Italy (population 49,218). The study was carried out from 1 September 1986 to 31 August 1989. There were 375 patients who were registered with a first ever stroke, with a crude rate of 2.54 (95% confidence limits 2.29-2.81) per 1000 per year; the rate adjusted to the European population is 1.55 (CL 1.36-1.77). The age adjusted relative risk for males is 1.35 (CL 1.10-1.66). Up to 15% of the patients were not admitted to hospital during the acute phase of their disease. At least 286 (76.3%, CL 72-80.6) of the cases were due to cerebral ischaemia; in 56 of these (19.6%, CL 15-24.2) a clinical diagnosis of lacunar ischaemia was made. The 30 day case fatality rate was 20.3% (CL 16.2-24.3); between one and six months 7.5% (CL 5-10.6) of patients died.