Since 1966, we have performed 41 renal transplants from unrelated living donors (ULD), 39 of which were "emotionally related". All donor-recipient pairs included in the present series were AB0-compatible. Recipients included 37 with primary and 4 with secondary transplants; 2 of the latter were diabetics. We compared these results to those of 41 recipients of cadaver donor kidneys matched for age, sex, immunosuppressive regimen, rank, and year of transplant, focusing our attention on the subgroups of patients under cyclosporin A (CyA) therapy (n = 24). We found that ULD transplantation was as successful as cadaver transplantation with good HLA matching: at 3 years, graft survival rates were 81% in ULD versus 86% in the control group under CyA. Moreover, grafts from ULD functioned more rapidly (no post-transplant dialysis and 70% of the patients with serum creatinine below 2 mg/dl within 3 days post-transplant). Graft tolerance was equivalent in both groups (50% of the patients experienced no rejection). We conclude that despite poor HLA matching, ULD transplantation with CyA as the basic immunosuppressive agent offers good results: benefiting from the quality of living donor kidney grafts, it helps to alleviate the persistent shortage of cadaver donors.