The MONICA Project is an international research program coordinated by WHO. It aims at studying the relationships of simultaneous temporal variations during a 10-year period a) of a morbidity index (acute myocardial infarction) and of the risk factors levels and b) of mortality indexes (lethality of acute infarction and coronary mortality) and of the medical care level. The study of the relationships will take into account the temporal variations measured in the numerous centers participating in the Project. It uses the methodology of registers completed by population studies and studies among patient cohorts. The whole methodology is standardized by a permanent quality control. A French participation (MONICA-France Project) includes 3 registers (Bas-Rhin, Haute-Garonne, Lille) with a national coordination and an autonomous analysis. The MONICA Project must provide public health information and should suggest hypotheses, but it must also be a "tool for research".