In patients with acute myocardial infarction, intravenous streptokinase therapy recanalizes 40% to 45% of occluded coronary arteries and reduces mortality by 25%. Recombinant tissue-type plasminogen activator (rt-PA) therapy is more potent for coronary arterial thrombolysis, producing both more rapid and more frequent (65% to 70%) reperfusion. Side effects (mainly reocclusion and bleeding) of streptokinase and rt-PA therapy are not markedly different. Whether the higher efficacy of rt-PA therapy will translate into a comparably larger reduction of morbidity and mortality remains to be determined in large comparative clinical trials. Both agents are available for clinical use. At present, the choice of agent for treating acute myocardial infarction must be based on consideration of the lower cost of streptokinase therapy compared with the established higher efficacy of rt-PA therapy for coronary recanalization.