The goal of this study was to compare the clinical presentation and angiographic morphology of patients having an unstable angina pectoris. A total of 321 patients were consecutively studied and underwent cardiac catheterization, mean age 59 + 6 years. According to Braunwald classification, class III was predominant (58%) On coronary angiography, 148 patients had single vessel disease, double-vessel in 92 and triple-vessel in 64. Morphology of coronary artery lesions was classified according to Ambrose's classification, 100 patients had simple lesions (type I or IIA), 204 patients had complex lesions (type IIB, III, intracoronary thrombus or total occlusion). Thoracic rest pain (class III) or postinfarction angina (class C), were associated with the presence of complex lesions. This subgroup of high risk patients would benefit from either Glycoprotein IIb/IIIa blockers with an early revascularisation strategy.