In acute myocardial infarction, the earlier intravenous thrombolysis is performed the more effective its action. Pre-hospital intravenous thrombolysis with 100 mg rt-PA was carried out in 49 patients within 3 hours of myocardial infarction. Male preponderance was conspicuous with 44 men (92%) and only 5 women (8%). Mean age was 50.2 +/- 8 years. The infarction was inferior in 48% of the cases. Out of the 49 thrombolyses performed by the mobile intensive care unit, 3 were discontinued on admission (2 diagnostic errors, 1 external heart massage). The time gained by pre-hospital thrombolysis was 52 +/- 25 minutes. There were few complications of thrombolysis: blood effusion at the site of puncture occurred in 4 cases (9%) and haematemesis in 1 case (2%). No cerebral or lethal haemorrhage was observed. Major complications of MI were seldom encountered at the pre-hospital phase: 1 patient died of extensive anterior necrosis with left ventricular dysfunction, and 2 had reversible ventricular fibrillation before treatment was initiated. There was no haemorrhagic complication. The earlier the patient was treated the lower the mortality and morbidity rates. Pre-hospital thrombolysis therefore seems to be feasible when performed by a mobile intensive care unit, and it represents an important gain of time.