The effects of a single oral dose (20 mg) of a new vasodilator, nicorandil, on exercise performance were assessed in 29 patients with stable effort angina using a symptom-limited treadmill exercise test. A single-blind, placebo-controlled, randomized, crossover design was employed. Compared with placebo, 20 mg of nicorandil significantly increased maximal exercise duration and time to 1 mm of ST-segment depression at 1, 3, and 6 h after administration. Systolic blood pressure was reduced both at rest and during exercise. Heart rate increase during exercise did not differ significantly compared with control, though resting heart rate was increased. The maximal pressure-rate product at peak exercise was increased in association with increased exercise time in about half of the patients, while it was unchanged or decreased in the others. It was suggested that nicorandil may act by either reducing myocardial oxygen demand and/or increasing myocardial oxygen supply.