Human immunodeficiency virus infection can affect the entire gastrointestinal tract and hepatobiliary system. Gastrointestinal abnormalities in acquired immunodeficiency syndrome are common and may relate to opportunistic inections and tumors, diseases which are usual in the anti-HIV negative population also, and disease of unknown aethiology, such as wasting syndrome and recurrent diarrhoeal illness. Diarrhoea and weight loss are found in more than 50% of patients with AIDS. Gastrointestinal manifestations range in severity from the discomfort of oral and perianal infections, through life threatening diarrhoea due to intestinal cryptosporidiosis. The approach to the patient with AIDS and gastrointestinal or hepatobiliary disorders is oriented toward diagnosing treatable aethiologies and avoiding unnecessary invasive procedures. Although the final prognosis of full developed AIDS is poor, management of gastrointestinal disease may be improved by accurate diagnosis.