A primary failure rate to achieve reperfusion by thrombolytic therapy in acute myocardial infarction of 20-40%, an early reocclusion rate of 5-20%, as well as an increased risk of bleeding that excludes many patients from this form of therapy are today considered main problems. Better application of conventional thrombolytic agents, new conjunctive therapies and development of improved plasminogen activators are investigated with the aim of minimizing these problems.