The influence of body mass index (BMI) on outcome of simultaneous pancreas-kidney transplantation (SPK) has not been well described. We retrospectively reviewed 88 consecutive primary SPKs performed at our institution between March 15, 1995 and August 28, 2001. All patients received antibody induction and maintenance immunosuppression with tacrolimus, mycophenolate mofetil, and steroids. Systemic-enteric implantation was performed in all patients. Primary end points were patient, pancreas, and kidney survival. Secondary end points were rates of anastomotic leakage, pancreas thrombosis, major infection, rejection, repeat laparotomy, and length of hospital stay. Values are shown as mean+/-standard deviation, range, or percentage. Fifty-two patients (59.1%) were nonobese with a BMI < or =24.9 (mean 21.7+/-2.2, range 15.4 to 24.9). Thirty-six patients were mild to moderately obese with a BMI > or =25 (mean 27.7+/-2.2, range 25 to 35.1). Distribution of recipient age, sex, and ethnicity was similar between groups. Kidney and pancreas preservation times were similar between nonobese and obese patients. One-, three-, and five-year actuarial patient (nonobese: 95%, 95%, 95% vs. obese: 95%, 95%, 89%), kidney graft (nonobese: 91%, 91%, 87% vs. obese: 97%, 91%, 85%), and pancreas graft (nonobese: 78%, 78%, 73% vs. obese: 70%, 62%, 62%) survival were comparable between nonobese and obese (P=NS). The mean rates of pancreas thrombosis, major infection, pancreas rejection, kidney rejection, relaparotomy, and length of hospital stay were similar in the two groups. The overall duodenojejunal anastomotic leakage rate was 8%. Obese patients had a 17% incidence of leakage (6 of 36) compared to a 2% incidence of leakage in nonobese patients (P=0.012). Six of seven leaks occurred in obese patients. Mean BMI in the seven patients with a leak (27+/-1.9) was significantly higher than in patients who did not develop a leak (24+/-3.7; P=0.05). Although obesity had no effect on patient or graft survival, it was associated with a significantly higher leakage rate. There should therefore be a higher degree of suspicion for the presence of duodenojejunal anastomotic leaks in obese SPK recipients.