It is not known whether coronary vasospasm is associated with coronary thrombosis. In this study, plasma levels of fibrinopeptide A during anginal attacks in 24 patients with variant angina were examined. A hyperventilation test was used to induce angina. Hyperventilation induced angina and ST segment elevation (AST: 0.32 +/- 0.14 mV, p less than 0.01) in eight patients with variant angina. Fibrinopeptide A increased from 0.75 +/- 0.27 at control to 7.8 +/- 4.4 ng/ml (p less than 0.01) during anginal attacks in these eight patients. In addition, four patients had spontaneous attacks of angina; they also had elevated levels of fibrinopeptide A during attacks (from 2.0 +/- 1.2 at control to 21.9 +/- 18.0 ng/ml [p less than 0.01] during attacks). Hyperventilation did not induce either angina or ST segment elevation in 12 of the patients with variant angina. Fibrinopeptide A levels did not change with hyperventilation in these patients. To determine whether elevated plasma levels of fibrinopeptide A were associated with angina, the plasma levels of fibrinopeptide A were examined during exercise-induced angina in seven additional patients with stable effort angina. They all developed angina with treadmill exercise; however, plasma fibrinopeptide A did not change. Therefore, only the patients with variant angina demonstrated elevated levels of fibrinopeptide A during anginal attacks. These findings suggest that coronary vasospasm associated with myocardial ischemia may induce stasis of blood, resulting in fibrinogen-fibrin conversion in the coronary vessels.