Various lesions of the liver commonly observed in renal transplant recipients are usually considered as a consequence of the transplantation procedures (immunosuppression, drug toxicity, alteration of immune responses to various viruses). A group of 64 patients all treated with corticosteroids and azathioprine was studied prospectively, and serial liver biopsies were performed on the day of transplantation and at 1 and 3 years after transplantation. Chronic hepatitis was already present in 40% of the patients on the day of transplantation and an increase of only 15% in the frequency of this condition was observed 3 years later. The presence of HBsAg in 45% of the patients at the time of transplantation was significantly associated with liver lesions. In about 3% of the cases, transplantation was directly responsible for a liver disease (peliosis hepatitis). During the followup period an evolution from chronic persistent hepatitis to chronic active hepatitis was observed with an abnormally high frequency (25%). We conclude that most of the liver diseases observed in transplant recipients are the consequence of events before transplantation and probably related to hemodialysis.