Gastrointestinal (GI) involvement is common in patients with acquired immunodeficiency syndrome; however, opportunistic disorders are generally not seen until the CD4 count falls below 200 cells/μl. Although any part of the gastrointestinal tract can be affected, the most common parts involved are the oesophagus and colon. Common oesophageal manifestations are dysphagia and odynophagia, caused by organisms such as Candida and cytomegalovirus (CMV). Common infectious and opportunistic disorders affecting the colon are Salmonella, Shigella, Campylobacter and CMV, which can result in diarrhoea, rectal bleeding and abdominal pain. Endoscopy is the preferred invasive procedure to diagnose most GI diseases. The main advantages of endoscopy are direct visualization of the entire GI tract, the option to obtain mucosal biopsy (which is often necessary to establish a specific diagnosis), and the ability to perform endoscopic therapy (e.g. injection of bleeding vessels). Therapy is based on the individual organism demonstrated.