Coronary thrombolysis with plasminogen proactivator, GE-0943, was undertaken in patients with acute myocardial infarction and compared with urokinase. Fifty patients were given 6000 units of GE-0943 intracoronary and the totally occluded infarct-related arteries were recanalized in 92.0%. Fifty-four patients who were given 3000 units of GE-0943 intracoronary demonstrated a recanalization rate of 68.2%, while intracoronary administration of urokinase in 54 patients showed a recanalization rate of 70.4%. There was only one patient with hemorrhagic complication among GE-0943 3000-units group, none among GE-0943 6000-units group, and 5 among urokinase group. Thus, intracoronary administration of GE-0943 is very effective and safe with a dose up to 6000 units.