We report the long-term follow-up (greater than 1 year) of 46 patients (12 pediatric) randomized to receive OKT3 for the first 14 days after OLT with low-dose steroids compared with 39 patients (8 pediatric) who received cyclosporine, steroids, and azathioprine. The mean period of follow-up for survivors was 648 +/- 261 days for the OKT3 group and 682 +/- 216 days for the cyclosporine group. Of the OKT3 patients, 46% were rejection-free in the first month compared with 31% of CsA-treated patients (P = NS). Rejection occurred after 1 month in 21% of the OKT3 group patients compared with 19% of the CsA group patients. One patient in each group developed vanishing bile duct syndrome. Eight patients in the OKT3 group and 13 in the CsA group experienced steroid-resistant rejection and required OKT3 rescue. In the 8 patients in whom OKT3 was reused, 4 had a positive ELISA after prophylaxis, and in 6, CD3-positive cells were greater than 10% during OKT3 reuse. Five patients resolved the episode. Of patients receiving OKT3 prophylaxis, 39% developed anti-OKT3 antibodies. In the OKT3 group 83% of patients and in the CsA group 75% currently have normal liver function. There was no difference in serum creatinine for either adult or pediatric recipients at 12 months in the two groups. Eight episodes (2 CMV) of severe infection occurred after 1 month in the OKT3 group compared to 11 (4 CMV) in the CsA group. Graft survival, 63% for the OKT3 group and 73% for the CsA group, and patient survival, 67% for the OKT3 group and 84% for the CsA group, were not significantly different in the two groups. We recommend reserving the use of OKT3 for resistant rejection or when cyclosporine is contraindicated, as we can show no long-term benefit from its routine prophylactic use.