Within the last decade, it has been appreciated that the acute coronary syndromes of unstable angina, non-Q-wave, and Q-wave myocardial infarction often share a common pathogenesis based on plaque disruption and thrombosis. Such "acute" lesions frequently have a characteristic angiographic appearance with sharp overhanging edges, irregular borders, and intraluminal lucency. This review focuses on the benefits and limitations of qualitative assessment of coronary lesion morphology, with respect to the sensitivity, specificity, and prognostic significance of complex lesions and intracoronary thrombi. Angiographic findings following thrombolysis for unstable angina are discussed, as well as the possible role for thrombolytic therapy as an adjunct to angioplasty in unstable angina.