Thrombolytic therapy has recently gained ascendance as an accepted form of treatment for acute myocardial infarction. Since the majority of patients with acute infarction have an occlusive coronary thrombus, plasminogen activators administered to these patients generate plasmin that proteolysis the fibrin elements of the thrombus and thereby reestablishes coronary patency. In addition to the conventional agents streptokinase and urokinase, newer, more fibrin-selective plasminogen activators are currently available for use or study, including tissue plasminogen activator and pro-urokinase. In acute myocardial infarction, the agents that have been studied most extensively are streptokinase and tissue plasminogen activator. Among the major recent studies of the use of these activators, several important observations have been made, including the need for administration of agent within 3 hours of the onset of pain, the efficacy of the intravenous route of administration, significant reduction in mortality with early administration, and significantly improved left ventricular function with early administration. Haemorrhagic complications remain a problem, but with judicious dosing their incidence can be kept to a minimum. Early studies in patients with unstable angina suggest that plasminogen activators may also have a role in the management of this clot-dependent disorder.