As part of a randomised multicentre study, 16 patients with acute myocardial infarction were treated with either anisoylated plasminogen streptokinase activator complex (APSAC) administered as an intravenous bolus of 30U or 250,000U of streptokinase by the intracoronary route. The reperfusion was documented angiographically during a 90-minute period and possible reocclusion was assessed at 90 minutes and 24 hours after the start of therapy. The percentage of reperfusion obtained in the APSAC group was 83% versus 63% in the streptokinase group. One reocclusion was seen after 24 hours in the APSAC group. Fibrinolytic activity was more pronounced in the APSAC group but there were no major bleeding problems in either group. The administration of 30U of APSAC by an intravenous bolus injection produced results at least as good as those obtained with intracoronary streptokinase and in addition offered the advantage of a simpler and quicker administration.