The favorable response to nitrates in the case of coronary heart diseases is based on both reduction in left ventricular pre- and afterload and improvement in coronary flow. These effects were studied in the setting of a long-term ISDN therapy with reference to the prognosis of patients after myocardial infarction. Following acute treatment in the respective hospitals, 608 patients with myocardial infarctions were allocated to two double-blind treatment groups with different ISDN dosage levels (group 1 = 5 x 2.5 mg i.d.; group 2 = 5 x 40 mg i.d.) and followed up over a period of 2 years. No differences were found with regard to the end points sudden cardiac death, reinfraction, and indication for revascularization. There was, however, a more frequent additional administration of calciumantagonists to patients of the low-dose group (p less than 0.05), a more frequent drop-out due to the lack of beneficial therapeutic results, and a more exceptional drop-out due to side effects in patients treated with low doses of ISDN (n.s.). The absence of any significant difference with regard to the end points might be attributed to; 1) a loss of potency of high-dose ISDN and simultaneous ineffectiveness of low-dose ISDN; 2) an efficacy of low doses; 3) an absence of actual influence on the target parameters, and 4) an inadequate follow-up time period.