We reviewed the effectiveness of Muromonab-CD3 (OKT3) and anti-thymocyte globulin (ATG) in the treatment of corticosteroid-resistant acute renal allograft rejection in 49 transplanted children. Reversal of rejection was successful in 22 of 23 patients (96%) treated with OKT3 and 21 of 26 (81%) treated with ATG (P = NS). Re-rejection episodes occurred within 1 month of cessation of therapy in 9 of 22 patients treated with OKT3 but only in 2 of 21 who received ATG (P < 0.05). In the patients with re-rejection, 7 of the 9 patients originally given OKT3 and 1 of the 2 who received ATG responded to a repeat course of high-dose corticosteroids; thus, at 1 month post treatment, the incidence of graft loss due to initial rejection or re-rejection was 13% for the OKT3 and 23% for the ATG group (P = NS). Graft survival was similar at 6 months: 82% for OKT3- and 73% for ATG-treated patients (P = NS); 100% patient survival was noted in both groups. Mean calculated creatinine clearance prior to, during, and at 1 and 6 months post rejection was similar in the OKT3- and ATG-treated groups. Neutropenia and thrombocytopenia occurred more frequently in the ATG group, but there was no significant difference in infectious complications. Two patients developed high (> or = 1:1,000) OKT3 antibody titers. In our experience, children with corticosteroid-resistant acute renal allograft rejection treated with OKT3 and ATG had similar allograft survival and level of renal function at 1 and 6 months, and number of infectious complications post therapy.