Patients with the acquired immune deficiency syndrome (AIDS) frequently develop hepatic dysfunction. Although hepatic injury may indirectly result from malnutrition, hypotension, administered medications, sepsis, or other conditions, the hepatic injury is frequently due to opportunistic hepatic infection, directly related to AIDS. Infection with Mycobacterium avium intracellulare typically occurs in patients with advanced immunocompromise and with systemic symptoms due to widely disseminated infection. In contrast, hepatic tuberculosis often occurs with less advanced immunocompromise. Cytomegaloviral infection may produce a hepatitis. Cytomegaloviral and cryptosporidial infections have been implicated as causes of acalculous cholecystitis and of a secondary sclerosing cholangitis. About 10-20% of patients with AIDS have chronic hepatitis B infection. These patients tend to develop minimal hepatic inflammation and necrosis. The clinical findings in patients with hepatic cryptococcal infection are usually due to concomitant extrahepatic infection. Hepatic histoplasmosis usually develops as part of a widely disseminated infection with systemic symptoms. Hepatic involvement by Kaposi's sarcoma is rarely documented ante mortem because an unguided liver biopsy is an insensitive diagnostic procedure. Patients with non-Hodgkin's lymphoma of the liver typically have lymphadenopathy, hepatomegaly, and systemic symptoms. As a pragmatic approach, patients with liver dysfunction and HIV-related disease should have a sonographic or computerized tomographic examination of the liver. Patients with dilated bile ducts should undergo endoscopic retrograde cholangiopancreatography because opportunistic infection may produce biliary obstruction. Patients with a focal hepatic lesion should be considered for a guided liver biopsy. Patients with a significantly elevated serum alkaline phosphatase level should be considered for a percutaneous liver biopsy. When performed for these indications, liver biopsy will demonstrate a significant disease involving the liver in about 50% of patients with AIDS and in about 25% of patients who are HIV seropositive but who are not known to have AIDS. The clinical impact of a diagnostic biopsy is blunted by a lack of efficacious therapy for many opportunistic infections.