The response of the coronary artery to a small dose (0.01 mg) of ergonovine was observed in nine patients without variant angina and in 10 patients with variant angina. Coronary angiograms were obtained before and after small and larger (routinely used) doses of ergonovine. With the larger dose, all 10 patients with variant angina had total or subtotal spastic occlusion accompanied by angina and ECG changes. Excluding the site of spastic occlusion produced by the larger dose of ergonovine, diameters of proximal, middle, and distal segments in each major coronary artery were measured before and after a small dose of ergonovine. The mean percentage of change in diameter (diameter before - diameter after a small dose of ergonovine)/diameter before a small dose of ergonovine X 100% in patients without variant angina was not significantly different from that in patients with variant angina (5.2 +/- 9.5% vs 7.0 +/- 11.9%, respectively). However, in patients with variant angina, a small dose of ergonovine produced a percentage of change in diameter of 39.8 +/- 15.3% at the site of spastic occlusion included by a larger dose of ergonovine, compared with that of 7.0 +/- 11.9% in the remaining non-spastic coronary arteries (p less than 0.05). These results indicate that patients with variant angina have local segments which respond differently to ergonovine from the remaining segments of coronary arteries. Clinically, this observation might be helpful in determining the angiographic positivity to ergonovine.