Recipient sex had no effect on first cadaver kidney transplant survival. In cadaver regrafts performed prior to 1984, male recipients consistently had lower 1-year graft survival than female recipients. Since 1984 there has been no difference associated with recipient sex. 2. Female donor kidneys had poorer graft survival rates than male donor kidneys. This difference became significant in first cadaver transplants since 1983 and was more evident in retransplants. The difference in regraft survival rates associated with the donor's sex has been dramatically reduced in more recent transplants if the projected results from 1989 transplants are correct. 3. Use of cyclosporine (CsA), pretransplant transfusions, and HLA-A,B mismatches independently contributed to the poorer survival rates of female donor kidneys. A large component of the donor sex effect may have been related to CsA toxicity. 4. Broadly sensitized (greater than 50% PRA) recipients of first transplants had 8% lower 1-year graft survival rates when they received a female donor kidney. 5. Female donors between the ages of 36 and 45 years yielded significantly lower 1-year graft survival rates in recipients of both first transplants and regrafts. This may represent a special donor risk group.