A single-blind study (n = 59) was performed to assess the effect of long-term (4 week) orally administered molsidomine (2 mg 4 X daily), isosorbide dinitrate (10 mg 4 X daily), and placebo on exercise tolerance performed on the bicycle ergometer by patients with stable angina on effort and with significant coronary artery disease. Isosorbide dinitrate had similar effects to placebo, both failed to modify the pressure-rate product, the sustained work load, and the ST segment depression, but slightly decreased, although not significantly, the incidence of angina. Although not affecting the pressure-rate product and the mean blood pressure, molsidomine decreased significantly the ST segment depression (p less than .05). In conclusion, by markedly reducing preload and because of its long-lasting effect (up to 6 h), the new vasodilator drug molsidomine plays a useful role in the long-term management of stable angina on effort.