Previous clinical and angiographic/histopathologic correlative studies have demonstrated that angiographic findings of occlusive thrombus, intraluminal filling defects and complex lesion morphology indicate the presence of intracoronary thrombosis. The purpose of this study was to determine whether the presence of these descriptors of intracoronary thrombosis is associated with the syndrome of prolonged rest angina. The coronary angiograms of 50 patients with prolonged rest angina without myocardial infarction (group I) and 42 concurrent patients with stable angina (group II) were reviewed without knowledge of the clinical syndrome. Patients with prior myocardial infarction, coronary angioplasty or coronary artery bypass graft surgery were excluded, as were patients with important aortic stenosis. Each coronary artery stenosis in a major epicardial vessel was evaluated for the presence or absence of intracoronary thrombus (defined using standard criteria), complex lesion morphology (defined as the presence of haziness, a smudged appearance or irregular lesion margins) and eccentricity, and the frequency of each of these findings in groups I and II was compared. Intracoronary thrombus was present significantly more often in group I patients (42%) than in group II patients (17%) (chi 2 5.77; p less than 0.02). Complex lesion morphology was also present significantly more often in group I (44%) than in group II (14%) patients (chi 2 8.17; p less than 0.01). Either standard criterion for intracoronary thrombus or complex morphology was present in 70% of group I but only 21% of group II patients (chi 2 19.7; p less than 0.001). These results support a strong association of the angiographic descriptors of intraluminal thrombosis with the clinical syndrome of prolonged rest angina.(ABSTRACT TRUNCATED AT 250 WORDS)