Thirty episodes of presumed infectious esophagitis in immunocompromised patients were investigated by means of esophagoscopy. Indications for esophagoscopy included dysphagia, odynophagia, and retrosternal pain. Factors potentially predisposing patients to esophagitis included previous exposure to radiation, recent cytotoxic chemotherapy, recent antibiotic therapy, corticosteroid therapy, and neutropenia. Sixteen of the 18 barium esophagograms done before esophagoscopy was performed revealed abnormalities; in 14 cases the results were consistent with infectious esophagitis. Abnormalities were noted during 27 of 30 esophagoscopy procedures. Visual findings were consistent with candidal esophagitis in 18 cases, with viral esophagitis in four, and with both in one. Specific infectious diagnoses were established by culture or histology in 17 episodes: 12 of candidal esophagitis, two of herpes simplex esophagitis, two of concomitant candidal and herpetic esophagitis, and one of enteroviral esophagitis. Specific noninfectious diagnoses were made in two episodes, and the esophagus was found to be normal in three. No specific diagnosis was made in eight episodes although visual examination indicated the presence of esophagitis. The only postesophagoscopy complications recorded were isolated episodes of spiking fever in three patients. In this compromised-host population with presumed infectious esophagitis, esophagoscopy resulted in a rapid and specific infectious diagnosis in 57% of episodes.