A total of 112 recipients of haploidentical live-related donor kidney transplants were assigned randomly prior to transplantation to two groups of immunosuppressive treatment. The first group (54 patients) received the conventional immunotherapy of azathioprine (AZA) and prednisolone (P; AZA-P group). In the second group, 58 patients were given cyclosporin (Cs) and P (Cs-P group). All patients had previous third-party blood transfusions. The follow-up period ranged from 3 to 6 years (mean 50 +/- 8 months) during which 13 patients (24%) in the AZA-P group and 6 (10%) in the Cs-P group were switched to the alternate immunotherapy (p > 0.05). Analysis of patient and graft survival along the follow-up period did not disclose significant differences between patients of the two groups. While the overall frequency of acute rejection episodes was not significantly different between the two treatment groups, the number of patients who had 2 or more rejection episodes was higher in the AZA-P group (p < 0.04). The mean serum creatinine levels were significantly higher in the Cs-P group than corresponding levels in the AZA-P group at 1, 12 and 24 months after transplantation. We have concluded that at least 75% of the haploidentical human lymphocyte antigen mismatched live-related donor renal transplants can be maintained on AZA-P immunotherapy with a comparable degree of success to those treated with Cs-P. However, in at least 15% of patients with conventional immunotherapy, Cs could reverse ongoing rejections, and therefore, it can be considered as a rescue treatment in AZA-treated patients with steroid-resistant or ongoing rejections.