Efficacy of reperfusion therapy in acute myocardial infarction is strictly time dependent. As is evidenced by several studies, most benefit in terms of myocardial salvage and short- and long-term mortality is achieved with initiation of therapy within the first 60-90 minutes after onset of symptoms. Nearly exclusively, prehospital initiation of thrombolysis makes it possible to take advantage of this early time window. Moreover a time gain of more than 30 minutes, up to 130 minutes, is possible by prehospital initiation of thrombolysis, depending on local circumstances. Randomized studies yielded a better outcome when a time gain of > or = 90 minutes was achieved. Since it has been shown that prehospital diagnosis of an acute myocardial infarction is reliable and out-of-hospital initiation of therapy has no additional specific risk, patients seen within the first 60-90 minutes after onset of symptoms or for whom a relevant time gain of > or = 90 minutes can be expected are ideal candidates for, and therefore should receive, prehospital thrombolysis.