Pancreas after kidney (PAK) transplantation, associated with a persistent elevation in serum creatinine (defined as a >25% increase from baseline), was seen in 7 of 11 (64%) cases maintained on immunosuppressive therapy consisting of tacrolimus, mycophenolate mofetil, and prednisone. Patients were converted to sirolimus as a means of minimizing or eliminating exposure to tacrolimus, the presumed nephrotoxic agent. With the use of sirolimus-based immunosuppression, and with elimination or minimization of tacrolimus, renal function, as measured by serum creatinine, stabilized or improved in all cases.