Travelers' diarrhea occurs when persons move from industrialized regions to developing countries with reduced hygiene. Bacterial enteropathogens from ingested food are the primary causes. Although it is possible to reduce the occurrence of illness by careful selection of food and beverages, travelers do not seem willing to restrict their diets. Diarrhea is associated with a disability of 24 hours per episode, interfering with travel plans and, of even greater concern, post-diarrhea irritable bowel syndrome (IBS) occurs in up to 10% of patients. The use of rifaximin, a poorly absorbed drug, is likely to become common as an attempt to prevent diarrhea and post-infectious IBS. All travelers to high-risk areas should take with them an effective antibacterial drug (rifaximin, fluoroquinolones, or azithromycin) for self-treatment of diarrhea occurring during travel. Additional work is needed to improve the hygienic conditions found in the developing world into which susceptible persons travel.