An effective therapy with coumarin derivatives within the secondary prevention after acute myocardial infarction makes great demands on the dispensary care. The risk of serious complications is relatively high. The risk of therapy with acetyl salicylic acid (ASS) in low dosage is significantly smaller. A significant decrease of the rate of reinfarctions and lethality by acetyl salicylic acid was made evident. The retrospective evaluation of the duration of treatment and effectiveness of the therapy with anticoagulants in postinfarction patients (n = 260) had the following result: reduction of the anticoagulant therapy from 75% in the year 1985 to 35% in the year 1989. Increase of the acetyl salicylic acid therapy (250 mg/day) from 23% to 60% in the same period. Up to 1987 the average duration of treatment with anticoagulants was 61.2 +/- 33.6 months, since 1988 only 9.6 +/- 2.6 months. 80% of the patients had a temporary ineffective therapy with anticoagulants, 50% were transitorily in the therapeutic risk region. At present only patients with an increased thromboembolic risk received an obligatory anticoagulant therapy.