Rifaximin is a semisynthetic rifamycin which is not absorbed from the gastrointestinal tract. It has been available in Europe and other countries for several years, and has recently been approved for treatment of traveler's diarrhea in the United States. Because of its broad spectrum of antimicrobial activity, rifaximin has been used with success in the treatment of infectious diarrhea, hepatic encephalopathy, small intestinal bacterial overgrowth, inflammatory bowel disease, and colonic diverticular disease. Potential indications include the irritable bowel syndrome and chronic constipation, Clostridium difficile infection and bowel preparation before colorectal surgery. In this publication both the present and future clinical use of rifaximin as well as the pharmacology behind it are extensively reviewed. Compiling the latest information on this remarkably active antibacterial agent, it will be an essential resource for infectiologists, gastroenterologists, and digestive surgeons alike.