1. Rejection was the major cause of first cadaver transplant failure, accounting for 62% of failures in the first 3 years of data in the UNOS Scientific Renal Transplant Registry. 2. During the transplant hospitalization, 27% of recipients experienced 1 or more rejection episodes. The 1-year graft survival rate for patients with rejection was 65%, whereas for those who were rejection free at discharge, survival was 85%. Patients who remained rejection free through the first 6 months had a 1-year graft survival rate of 95%. 3. The incidence of early rejection decreased as the recipient's age increased. Only 18% of patients over 60 had rejection prior to their hospital discharge, and 33% of patients under 15 had early rejections. 4. The incidence of rejection was 20% for Hispanics, 27% for Whites, and 30% for Blacks. Despite the significant difference in early rejection between White and Hispanic recipients, there was no difference in the 1-year graft survival rate comparing these racial groups. Blacks had significantly poorer survival whether or not rejection occurred early than White or Hispanic recipients. 5. Sensitization had no apparent effect on the likelihood of early rejections for first transplant recipients, but graft survival was 54% for sensitized patients with rejection and 64% for nonsensitized rejection patients. 6. Prophylactic antilymphocyte antibody (ALG or OKT3) reduced rejections during the transplant hospitalization from 30% to 20%. Patients given ALG or OKT3 prophylaxis had a significantly higher incidence of rejection between discharge and 6 months than those who did not receive either treatment. There was no significant improvement in 1-year graft survival for patients treated with antibody.(ABSTRACT TRUNCATED AT 250 WORDS)