The influence of methyl ergonovine on coronary artery diameter and regional ventricular function was studied in three groups of patients with and without suspected coronary artery spasm. Ten patients with angina at rest in whom spasm was suspected were compared to seven coronary heart disease patients with stable effort angina. Six patients without coronary heart disease served as controls. Ergonovine, an agent known to cause coronary vasoconstriction, was administered in order to identify the possible role of spasm in the various subgroups. The standardized study procedure comprised coronary and left ventricular angiography before and after 0.1 to 0.4 mg ergonovine i.v. as well as after 1.6 mg nitroglycerin sublingually. Following ergonovine provocation, narrowing of the anterior descending branch averaged 22 per cent in the patient group with suspected spasm, 3 per cent in patients with coronary heart disease, and 6 per cent in the control group. The spasm group also displayed regional ventricular hypokinesis and an increase in endsystolic volume. LVEDP increased from 15 +/- 6 to 28 +/- 7 mm Hg (p < 0.0005) mean circumferential fiber shortening (mean Vcf) decreased from 1.6 +/- 0.4 to 1.1 +/- 0.4 circ/s (p < 0.0025), and the velocity of shortening in the anterior apical hemiaxis (Vm3) declined from 1.9 +/- 0.2 to 0.8 +/- 0.4/s (p < 0.0005). These changes were much less evident in the coronary heart disease group. No significant hemodynamic changes were observed in the control group. Patients with angina at rest are much more susceptible to ergonovine-induced coronary artery narrowing than patients with stable exertional angina.