Mechanical cardiac massage by a pneumatic device which fits over the ventricles of the heart was studied in six patients with cardiac arrest who failed to respond to conventional means of resuscitation. Adequate arterial blood pressure, full peripheral pulses, respiratory efforts, small reactive pupils, reasonable cardiac output, and a low venous pressure were obtained for as long as four hours. In a 48-year-old patient ventricular fibrillation did not respond to external or internal massage and defibrillation in 35 minutes, and there was no ECG activity. With this instrument the circulation was supported for an hour (blood pressure 135/50). Defibrillation was then possible, and the patient survived for six days, dying of her primary disease process, which was unrelated to the heart. These studies are being continued and indicate that this approach may be helpful for cardiac resuscitation, for prolonged circulatory support, and for maintaining the circulation in potential donors for organ transplantation.