We investigated the clinical, electrocardiographic and hemodynamic features and the prognostic implications of early spontaneous angina in 31 consecutive patients after acute myocardial infarction. Re-elevation of ST segments in the area of infarction occurred during angina and during reinfarction in all but one patient. Depression of ST segments, when present during pain, involved the same leads as in the acute infarction. Blood pressure and double product tended to increase during pain in 23 patients. The magnitude of this change, however, often varied from crisis to crisis and there were no increases in these parameters in one or more attacks in 15 patients. Sublingual nitroglycerin, 1.0 mg, failed to relieve one or all anginal episodes in 17 of the 28 patients in whom it was given. In-hospital mortality rate was 10% (3/31) and always followed reinfarction. In-hospital reinfarction rate was 16% (5/31) and followed a larger number of anginal crises (7.2 +/- 1.3 vs 3.0 +/- 2.1, P less than 0.001) and a higher incidence of transient hypotensive episodes than in the rest of patients (3/5 vs 3/26). Three additional patients died after discharge. Of the remaining 25 patients and during a follow-up of 26 months (16-34) only one developed reinfarction. Early resting angina after a transmural infarction is almost invariably associated with ECG evidence of ischemia in the leads overlying the infarcted zone. The inconsistent changes in blood pressure and heart rate during pain render these hemodynamic changes an unlikely cause of this form of angina. While postinfarction angina did not carry a grave short- or long-term prognosis, patients with recurrent crises demonstrated as high a risk of reinfarction and death as those with spontaneous hypotension.