1. Most of the first rejections occurred between the first and third weeks after transplantation, with the peak at 7 days. 2. Average serum creatinine values of 2 mg/dl were achieved in 2 days for living-related donor transplants. Cadaver donor grafts reached an average of 4 mg/dl by the tenth day, but in patients without rejection serum creatinine values of almost 2 mg/dl were achieved. 3. Cadaver donor grafts with cold ischemia times less than 12 hours led to the best early serum creatinine values. Cold ischemia times up to 48 hours and possibly beyond led to slightly higher creatinine levels but did not produce damage in proportion to the cold ischemia time. 4. Patients who were sensitized to more than 50% of the panel showed evidence of sensitization by having higher serum creatinine levels from one week to 3 weeks. 5. Even in the first few days after transplantation with a cadaver donor, black recipients had a higher serum creatinine than white recipients. The donor's race did not have a marked effect. 6. CsA doses given to cadaver donor recipients were about 2-4 mg/kg higher than living-related donor transplants. Patients experiencing a rejection episode were found to have been treated with about 1 mg/kg more than those without rejections. The corresponding blood levels of CsA were higher in the cadaver donor grafts and those with rejections. 7. Early serum creatinine levels were very strongly correlated with the one-year graft survival rate. Even one day after transplantation, the difference between patients with the best and worst one-day serum creatinine levels was as much as 30% in the one-year graft survival rate. At 2 weeks, the group with the best serum creatinine had a one-year survival rate that was 50 percentage points higher than the worst creatinine group. At one month, the best serum creatinine group had a one-year survival rate that was about 80 percentage points higher than the worst serum creatinine group. 8. Patients with high CsA levels of over 400 ng/ml in the early one-month posttransplant period, had poorer one-year graft survival than those with lower levels. The optimum level appeared to be less than 100 ng/ml by the tenth day and about 100-200 ng/ml to the third week posttransplant.(ABSTRACT TRUNCATED AT 400 WORDS)