During a five-year period, 178 patients had the intraaortic balloon pump (IABP) inserted for circulatory support. The IABP was used most frequently as an adjunct for weaning patients from cardiopulmonary bypass. Seventy-seven of 103 patients (75%) were successfully weaned from cardiopulmonary bypass with the IABP, and 36 of them (35%) ultimately survived hospitalization. Other indications for the IABP included circulatory support before cardiac operation (16 patients), operative prophylaxis in high-rish patients (13), and postoperative hemodynamic support (23). Additionally, the IABP was placed in 23 patients who did not undergo cardiac operation. The incidence of IABP-related complications was significantly less when the IABP was inserted through the ascending aorta (4%) intraoperatively compared with the femoral or iliac artery (25%) (p less than 0.05). This was due primarily to vascular complications and groin wound infections that occurred with the femoral or iliac artery approach. IABP-related spinal cord paralysis developed in 3 patients (1.7%). We conclude that the IABP is an effective support device for treating patients with left ventricular failure particularly when weaning them from cardiopulmonary bypass. However, the risk of complications, including paraplegia, must be carefully weighed when use of the IABP is considered, especially in situations in which its efficacy is less clear.