A retrospective review of 110 consecutive kidney transplants performed during 4 years revealed the development of renal artery stenosis in 9 patients (8.18%). A comparison of this group with a control group similar in patient age and interval elapsed since transplantation revealed no significant differences in donor and recipient ages, degree of HLA compatibility or serum creatinine levels. However, there was a significant difference in the number of acute rejection episodes. In our series only male patients were affected. A sizable proportion of the patients (50%) had no detectable murmur over the graft area despite high blood pressure and increased creatinine levels. The absence of surgical injury during extraction and implantation of the grafts, together with the anatomical site of the stenosis and correlation with the degree of immunological intolerance suggest an immunological factor as the underlying cause in post-transplant renal artery stenosis.