To assess the characteristics of chronic hepatitis in hepatitis B surface antigen (HBsAg) carriers with intrahepatic delta antigen, the hepatic histologic findings of 137 patients were reviewed; 101 patients were followed for 2 to 6 years. The predominant liver disease was chronic active hepatitis in 93 patients or cirrhosis in 32; minor forms of chronic persistent or lobular hepatitis were seen in 12 patients. Eight of the 26 patients with an initial diagnosis of cirrhosis died during the follow-up period. Cirrhosis developed in 31 of 75 patients (41%) without nodular regeneration seen in the first biopsy specimen; 5 of these patients died. Treatment with prednisone or azathioprine did not induce histologic amelioration of delta hepatitis or prevent cirrhosis. Chronic HBsAg hepatitis with intrahepatic expression of the delta antigen is an active, progressive disease unresponsive to conventional immunosuppressive treatment.