Monoclonal antibody (OKT3) is a powerful T-cell–specific immunosuppressive agent that has been used for induction therapy and to treat acute or steroid-resistant graft rejection episodes. Results of 43 steroid-resistant acute rejection episodes treated with OKT3 at our center between September 1994 and June 2004 were retrospectively analyzed. There were 36 male and 7 female recipients (mean age, 32.7 ± 11.6; range, 19-48 years) in the analysis. Seven kidneys were from cadaveric donors, and 36 were from living-related donors. This was the first kidney transplantation for all patients. Mean time between transplantation and OKT3 treatment was 7.2 ± 1.67 months. Nineteen patients received 10 doses, and 24 patients received 14 doses of OKT3. Acute rejection episodes responded to OKT3 therapy in 34 (79.06%) patients and graft functions improved; however, the remaining 9 (10.04%) patients failed to respond to OKT3 therapy. Four of the 34 patients who received OKT3 therapy required hemodialysis during follow-up. In the OKT3 responding group, the mean serum creatinine level decreased from 3.96 ± 2.5 mg/dL to 2.45 ± 1.77 mg/dL. Minor adverse effects, such as fever, dyspnea, tachycardia, and bradycardia were observed in 11 (25.5%) patients. Acute pulmonary edema occurred in 1 (2.3%), CMV infection in 1(2.3%), and bacterial infections in 8 (18.6%) patients. The 1-, 3-, and 5-year graft and patient survival rates were 88%, 65%, and 41%, and 94%, 86%, and 78%, respectively. Our data demonstrate that OKT3 should be used very selectively and carefully.