The initial studies in Europe with tissue-type plasminogen activator (rt-PA) have been coordinated by a European Cooperative Study Group. By February 1987, 258 patients had been entered into comparative coronary patency trials of rt-PA versus streptokinase and rt-PA versus placebo (trials completed and published); 123 patients had entered a coronary patency trial of prolonged rt-PA infusion versus short-term rt-PA infusion (trial completed but results not yet published); and greater than 500 patients had been recruited for left ventricular function and infarct size trials comparing rt-PA with placebo and rt-PA alone with rt-PA plus immediate coronary angioplasty (studies still in progress). The first three studies used two chain rt-PA, 0.75 mg/kg, for the rt-PA versus streptokinase and rt-PA versus placebo studies and 40 or 80 mg for the short-term versus long-term study. The current studies are using single chain rt-PA in a dose of 100 mg (20 mg bolus, 40, 20 and 20 mg in succeeding hours). Coronary patency at angiography 90 minutes after the start of treatment was 70% for rt-PA and 55% for streptokinase, 1.5 million units, in the plasminogen activator versus streptokinase study (p = 0.054), 61% for rt-PA and 21% for placebo in the rt-PA versus placebo study (p less than 0.001). In the first three studies (251 patients allocated to rt-PA) there was one case of retroperitoneal hematoma, one of hematemesis and no cases of cerebral hemorrhage; 38 patients (15%) had a hematoma or bleeding related to arterial catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)