Liver functional abnormalities were seen in 13 (19.7%) of 66 recipients of cadaveric renal homografts treated with cyclosporin A and prednisone. However, such presumed hepatotoxicity was a minor problem in the use of cyclosporin A. The complication was less frequent than that of nephrotoxicity, was as easily manageable with reductions in the cyclosporin A dosage, and generally did not cause clinical illness. In an occasional case, late hepatotoxicity can force a therapeutic change from cyclosporin A to azathioprine, but careful consideration should be given to the dangers of subsequent rejection.