The Transplant Service at the University of Minnesota Hospitals has performed over 2,000 kidney transplants. Fourteen of these patients have developed cardiac conditions necessitating surgical intervention at intervals of 9 to 144 months (mean 67 months) following their transplantation. These individuals had a mean age of 42 years, and five (36%) were diabetic. All patients had functioning renal allografts with preoperative serum creatine levels ranging from 1.0 to 1.8 mg/100 ml (mean 1.4 mg/100 ml). Ten patients underwent aorta-coronary saphenous vein bypass grafting. One patient underwent bypass grafting and concomitant left ventricular aneurysmectomy. Native valvular endocarditis developed in two patients. One had tricuspid valve debridement for fungal endocarditis and the other had aortic valve replacement for bacterial endocarditis. The final patient had calcific aortic stenosis and coronary artery disease necessitating aortic valve replacement and coronary bypass. Two patients (14%) died perioperatively. One was a young woman with juvenile-onset diabetes and preinfarction angina who died suddenly several days after the operation; at autopsy, she was found to have an occluded graft to the right coronary artery and extensive infarction. The other was a 54-year-old woman with calcific aortic stenosis, coronary artery disease, and unstable angina who died perioperatively of uncontrollable arrhythmias. Autopsy suggested that she may have had an unsuspected infarction 1 to 2 days before the operation. The remaining 12 patients had uneventful postoperative courses and returned to Class I functional status from a cardiac standpoint. There has been one late death (7%), 45 months after successful coronary artery bypass grafting, as a result of complications attendant to a perforated gastric ulcer. The remaining 11 patients are alive and well at intervals of 8 to 93 months (mean 31 months) after operation. Postoperative serum creatinine levels at hospital discharge averaged 1.6 mg/100 ml, not significantly changed from preoperative levels. Cardiac operations can be performed safely in patients with functioning renal allografts. Patient survival is acceptable and preservation of renal function has been uniformly successful in surviving patients.