In the GISSI trial, 11,712 patients with acute myocardial infarction were randomized to receive either standard care or standard care with 1.5 million units streptokinase intravenously. A highly significant reduction in mortality during hospitalization in streptokinase-treated patients was observed. The mortality at 1 year was determined in 98.3% of the patients who had been originally randomized; the 1 year mortality of patients discharged alive was similar in those patients treated with streptokinase and those who were not; that is, the beneficial effects of streptokinase treatment on survival that were observed in the hospital phase of the study persisted unchanged and with comparable statistical significance for 1 year. However, a higher incidence of reinfarction occurred in the treated versus the control groups both during the hospital phase and at the 6 month follow-up. Streptokinase treatment had no detectable effect in patients with a history of previous infarction.