Significant liver disease developed in 14 patients after renal transplantation. Nine patients had morphologic and functional evidence of chronic active hepatitis. In general, these patients had few symptoms of liver disease, even though the course of chronic active hepatitis was progressive. Despite large doses of prednisone, cirrhosis ultimately developed in five patients. The cause of chronic active hepatitis could not be related to azathioprine or methyldopa therapy because there was no perceptible change in the course of liver disease after treatment with these drugs was stopped. Three patients were persistently positive for hepatitis B surface antigen. Isolated instances of granulomatous hepatitis (Mycobacterium kansasii) and of prolonged intrahepatic cholestasis were encountered in patients with chronic active hepatitis. Two patients had acute cytomegalovirus hepatitis. There was one episode each of fulminant herpes simplex hepatitis and severe fatty metamorphosis.