To determine the safety of intraaortic balloon pump catheter insertion for critical coronary ischemia through suprainguinal prosthetic bypass grafts, we examined our experience of 19 intraaortic balloon pumps placed through grafts in 17 patients by means of surgical exposure (8) or the percutaneous (11) approach. Fourteen intraaortic balloon pumps were placed through matured grafts at a time remote (2 to 13 years; mean, 7 years) from their vascular bypass surgery. Five were inserted through nonmatured grafts during the same hospitalization as their vascular reconstructive surgery (1 to 12 days; mean, 4 days). One patient, a day after an aortoiliac bypass, died during an urgent, surgical intraaortic balloon pump insertion for cardiogenic shock. All other patients had prompt reversal of their cardiac ischemia. Decreased limb perfusion developed during use of the intraaortic balloon pump in three patients, all of whom had their intraaortic balloon pump placed percutaneously through mature grafts. Two of these required surgical thrombectomy. Ten intraaortic balloon pump insertions in eight patients survived the hospitalization and were followed for a mean of 24 months (range, 2 weeks to 64 months). No localized groin or graft infections were identified. No bleeding complications or pseudoaneurysms occurred. Thus in patients with unstable, severe, cardiac disease, intraaortic balloon pumps can be safely placed through indwelling suprainguinal bypass grafts.