Renal dysfunction, one of the most common complications after liver transplantation, influences patient outcomes. Little is known, however, about it in Korea. The aims of this study were to determine the incidence and to identify the risk factors for renal dysfunction after liver transplantation. Sixty-two patients who survived over 6 months after transplantation were enrolled. Renal function was classified by creatinine clearance (Ccr, mL/min), which was estimated using the Cockcroft-Gault formula. Twenty-seven patients (44%) showed mild renal dysfunction (60 < or = Ccr < 90), and 27 patients (44%), moderate dysfunction (30 < or = Ccr < 60). The others were found to have normal function (Ccr > or = 90). None displayed severe dysfunction (Ccr < 30). Compared to a control group (Ccr > or = 60), the renal dysfunction group showed lower preoperative Ccr (91 +/- 28.6, 63 +/- 21.9, respectively, P < .01) and lower Ccr at 3 months after transplantation (72 +/- 17.1, 49 +/- 14.6, respectively, P < .05). Age, sex, immunosuppressive drug usage, serum tacrolimus levels, and the frequency of postoperative acute renal failure did not affect the postoperative renal dysfunction. Twenty-six patients received mycophenolate mofetil while reducing the dose of calcineurin inhibitors because of compromised renal function. With mycophenolate mofetil treatment, the renal function seemed to improve, although the difference was not statistically significant (P = .057). These data demonstrate that renal dysfunction is common after liver transplantation and that preoperative renal function is the important factor predicting postoperative renal dysfunction.