Background and Purpose: In the stroke component of the WHO MONICA Project, community-based registers of acute stroke have been undertaken in 20 populations in Finland, Sweden, Denmark, Germany, Italy, Yugoslavia, Hungary, Poland, Lithuania, Russia and China. This paper reports on diagnostic procedures and management of acute stroke in these populations. Methods: The MONICA stroke registers apply uniform registration procedures and diagnostic criteria. Data for 3 years were pooled and used for cross-sectional comparisons. Longitudinal analyses of the use of computerized tomography (CT) scans and autopsy rates were based on all years up to 1990 for which information was available. The total population in the age range investigated (35–64 years) was 3,250,000. Strokes were also recorded for the 65- to 74-year age range in seven of the 20 populations. Results: In all populations, more than three quarters of all 35- to 64-year-old stroke patients were managed in hospital; in nine populations more than 90% were managed in hospital. The use of CT scans ranged from 0% in Russia to 70–76% in West Germany, Italy, Sweden and two of the 3 Finnish populations. During the mid 1980s, use of CT scan increased rapidly in China (Beijing), Denmark, Finland and Yugoslavia but spread only slowly in Poland, Lithuania and Russia. Autopsy rates varied from 0% in China to 76% in the Hungarian and one of the Russian populations. During the 1980s, autopsy rates were stable in most populations, but declined considerably in Lithuania, Poland and Sweden. Elderly patients (65–74 years) were less often hospitalized in China but this was not the case in European populations. In all populations, CT scan and autopsy were less often performed in older subjects. Conclusions: Large variations exist between countries in the use of diagnostic procedures and the management of acute stroke. Data obtained before the late 1980s permit only very limited multinational epidemiological comparisons of stroke subtypes, but the possibility of making such comparisons is rapidly impr