Switzerland is currently participating in the multicenter study "Monitoring of Trends and Determinants in Cardiovascular Disease - MONICA". Incidence of acute myocardial infarction will be studied over a period of ten years in a target population. The results will be compared with changes in medical care and the spread of known risk factors for cardiovascular disease in the population. This paper describes how the different data will be registered in Switzerland and how far the work has progressed up to now.