The optimal role of thrombolytic therapy in clinical practice has not been defined precisely. A review of available information indicates that such therapy may be useful in a small number of carefully selected patients with deep vein thrombosis and/or pulmonary emboli. The superiority of thrombolytic therapy over conventional surgery for arterial thrombi has not been convincingly demonstrated. Available evidence suggests such therapy should be reserved for those conditions in which surgery may be expected to have a poor outcome or be associated with a high incidence of complications. Preliminary information suggests thrombolytic therapy may be of benefit in selected patients with acute myocardial infarction.