Thirty-two patients who had remained ambulant and active after suffering an acute myocardial infarction were observed for 6 months. Complications were present initially in 11 but proved transient. One patient died of a new coronary thrombosis 15 weeks after the initial episode. There were no recurrences among the 31 surviving patients. After the 6 months all but two patients were as well as before the attack; 21 were free of symptoms and there was no undue incidence of objective findings that could be attributed to failure to rest after the attack. It is therefore concluded that, for patients who suffer an acute myocardial infarction, immediate diagnosis and admission to a coronary care unit need not be equated invariably with immobilization in bed. Our experience suggests that selected patients can be allowed moderate activity without ill effects and thus avoid the undesirable consequences of enforced bed rest.