We randomized 352 patients with suspected acute myocardial infarction (AMI) to treatment with rt-PA (n = 177) or placebo (n = 175). Patients were eligible if evaluated within 2 h and 45 min from onset of chest pain, and if aged less than 75 years. There were no ECG criteria for inclusion. A mobile coronary-care unit with a cardiologist present was used to initiate treatment at home in 29% of cases. During 1 year of follow-up the mortality in patients treated with rt-PA was 10.2%, as compared with 14.3% in patients the initial ECG, the mortality during the first year was 8% in the rt-PA group vs. 18% in the placebo group (P less than 0.05). Among patients without ST-elevation the mortality was 9% for the rt-PA group vs. 12% for the placebo group (NS). Requirement for rehospitalization, symptoms of angina pectoris and congestive heart failure, time of return to work and requirement for various medications did not differ significantly between the two groups, regardless of the initial ECG pattern.