Diarrhea is an exceedingly common complaint in patients with human immunodeficiency virus (HIV) infection, and the severity of symptoms ranges from mild, self-limiting diarrhea to debilitating disease that can result in malnutrition, volume loss, and shock. Up to 40% of patients with HIV infection report at least 1 episode of diarrhea in a given month, and approximately 1 quarter of patients experience chronic diarrhea at some point. The prevalence of diarrhea increases with decreasing CD4 counts. The clinical features, diagnosis, and management of diarrhea in patients with HIV are reviewed.