The aim of this study was to determine changes in treatment of myocardial infarction between 1986 and 1989 in the Haute-Garonne region and, in particular, to assess the role of aspirin and antiaggregant therapy. The cases of 416 patients admitted to hospital for myocardial infarction in 1986 and 1989 were reviewed. During this period the prescription of acetylsalicyclic acid during the acute phase of myocardial infarction increased threefold (26.4 vs 72.9%; p < 0.001) and fivefold when associated with fibrinolytics, coronary bypass or angioplasty. Similarly, the prescription of aspirin at the time of hospital discharge doubled (from 32.6 to 69.5%; p < 0.001). The dosage of aspirin decreased from 500 mg and more per day in 1986 to a dosage of 250 mg or 100 mg per day in 1989. The most commonly prescribed preparation is lysine acetylsalicylate. The hospital mortality in the Haute-Garonne between 1985 and 1989 has decreased as observed in the Haute-garonne centre of the MONICA project. During the same period, the prescription of aspirin in association with angioplasty, bypass surgery and fibrinolytics, has undergone a remarkable increase. The changes observed during this period of observation are in perfect accord with results already published of therapeutic trials of antithrombotic agents in the acute phase or the post-infarction period (ISIS 2).