25 patients with stable angina pectoris after acute myocardial infarction were given single and maintenance doses of isosorbide-5-mononitrate (IS-5-MN) in a controlled-release formulation. For evaluation of the efficacy of this treatment, a score based on exercise tests and patient's complaints including additional antianginal medication were used 4 weeks after the acute event. For assessment of anti-ischemic effect non-invasive parameters including heart rate, arterial blood pressure, changes in ST segments, frequency of premature ventricular beats and systolic time intervals were used before medication, 5 h after the initial dose and 7 days after maintenance therapy. The therapeutic concept of interval treatment was found to be effective. Nitrate tolerance did not develop. Measurements of plasma levels under steady-state conditions revealed minimum values of 100 ng/ml and maximum levels of 460 ng/ml which is in between the threshold for anti-ischemic effect and development of nitrate tolerance, respectively.