The German Cardiovascular Prevention Study (GCP) is a multicentre community-based intervention study for the primary prevention of ischaemic heart diseases (ICD-9 410-414) and cerebrovascular diseases (ICD-9 430-438). It comprises a total population of 1.23 million persons in five study regions spread all over the F.R.G. Prevention measures in overlapping campaigns to modify health behaviour and life styles are aimed at the cardiovascular risk factors of cigarette smoking, elevated blood pressure, hypercholesterolaemia, overweight, and physical inactivity over a period of eight years. Age-specific cardiovascular mortality in males and females aged 25-69 years in intervention regions shall be reduced by at least 8% as compared to the mortality experience of the rest of the Federal Republic. Official mortality statistics and incidence data in parts of the study population, together with proxy measures for case fatality, will be incorporated into the evaluation strategy. Risk-factor reduction is being assessed in three health examination surveys at the start, at mid-term and at the end of the study. Further information on the effectiveness of preventive measures is obtained by process evaluation and observation of structural changes in the communities.