A black male with known sickle cell trait (hemoglobin AS) received two cadaveric renal transplants in succession. After excellent initial graft function he had what appeared clinically to be an acute rejection episode which could not be reversed by immunosuppressive therapy on either occasion. The histopathology of the removed allografts did not reveal a picture of acute rejection, but instead revealed extensive intravascular sickling of the erythrocytes. This is important especially for the transplant centers in the United States which may have a significant number of the black population among the renal allograft recipients.