Despite the development of trained mobile rescue squads, cardiopulmonary collapse outside the hospital continues to carry a poor prognosis. We examined retrospectively the clinical courses of 19 consecutive coronary unit patients who had experienced prehospital cardiopulmonary resuscitation. Seven patients received basic life support from bystanders within five minutes. Cardiopulmonary resuscitation in the other 12 patients was delayed beyond five minutes pending the arrival of rescue personnel. Six of seven early-resuscitated patients survived compared with six of 12 late-resuscitated patients (P less than 0.01). The early-resuscitated patients were more alert on admission and had lower pulmonary pressures and higher cardiac outputs compared to the late-resuscitated patients. The early-resuscitated patients also had less residual central nervous system and myocardial damage on discharge than the late-resuscitated patients. On follow-up, three early-resuscitated patients had returned to full-time work compared with none in the late group. Training laymen to initiate early basic life support can benefit the cardiopulmonary collapse victim.