APSAC is a new thrombolytic agent with advantages over conventional therapy such as streptokinase. In particular, it is suitable for intravenous administration over 4 to 5 minutes, in contrast with the prolonged infusion required with intravenous streptokinase, thus facilitating treatment of acute myocardial infarction outside a coronary care unit. Additionally, its fibrinolytic action is theoretically selective for fibrin associated with thrombi, which should minimise systemic fibrinolysis. However, in practice, systemic fibrinolysis does occur to some extent in most patients, but clinically significant haemorrhagic complications are rare. At the recommended dose of 30U injected intravenously over a period of 4 to 5 minutes in patients with acute myocardial infarction of less than 6 hours' duration, reperfusion of occluded coronary arteries occurs in about 72% of patients (range 53 to 91% in individual studies). Subsequent reocclusion has been reported in 0 to 20% of patients in most studies, with an average reocclusion rate of around 10%. The reperfusion rate compares favourably with that reported for intracoronary streptokinase and has tended to be superior to that with intravenous streptokinase. Thus, APSAC is an important advance in thrombolytic therapy for patients with acute myocardial infarction. Of particular importance is its relative ease of administration, reducing the dependence on coronary care units with catheterisation facilities, and the associated costs and delays in implementing treatment. APSAC should result in effective thrombolytic therapy being rapidly introduced after acute myocardial infarction in a wider proportion of patients than was previously feasible.