The effect of nicorandil, a new coronary vasodilator, was evaluated in 32 patients with variant angina pectoris in a single-blind trial. The study was comprised of a pretreatment period of 2 days with a placebo, a 3-day nicorandil medication period (20 mg/day), and a 2-day posttreatment period with the placebo. Anginal attacks disappeared completely in 24 of the 32 patients. The number of attacks during the pretreatment period, 3.6 +/- 0.4 per day, became significantly reduced to 0.7 +/- 0.2 per day during nicorandil therapy (P less than 0.001) and significantly increased to 1.3 +/- 0.3 per day after withdrawal of the drug (P less than 0.05). In 17 patients with continuous ECG monitoring, the frequency of occurrence of ST-segment elevation was 8.6 +/- 2.7 per day during the preobservation period, significantly decreased to 0.4 +/- 0.2 per day during nicorandil therapy (P less than 0.01), and significantly increased to 1.9 +/- 0.7 per day after withdrawal of the drug (P less than 0.05). The results demonstrate the effectiveness of nicorandil in the treatment of variant angina pectoris.