We describe the incidence of and laboratory and clinical characteristics associated with Entamoeba histolytica/Entamoeba dispar infection diagnosed in human immunodeficiency virus (HIV)-infected persons enrolled in the Adult and Adolescent Spectrum of HIV Disease Project. From 1 January 1990 to 1 January 1998 (82, 518 person-years of follow-up), 111 patients (98% men) were diagnosed with E. histolytica/E. dispar infection. Among HIV-infected patients in the United States, the incidence of diagnosed E. histolytica disease is low (13.5 cases per 10,000 person-years [95% confidence interval, 7.7-22.2], with diagnosis most common in those patients exposed to HIV through male-male sex.