This is one of a series of statements discussing the practice of gastrointestinal endoscopy in common clinical situations. It is intended to aid endoscopists in determining the appropriate use of antibiotic prophylaxis for patients undergoing gastrointestinal endoscopic procedures. Guidelines for the appropriate practice of endoscopy are based on a critical review of the available data and expert consensus. Controlled clinical studies are needed to clarify aspects of this statement, and revision may be necessary as new data appear. Clinical consideration may justify a course of action at variance from these recommendations. Recommendations on prophylaxis against infective endocarditis were developed in conjunction with the Committee on Rheumatic Fever, Endocarditis and Kawasaki Disease of the Council of Cardiovascular Disease in the Young of the American Heart Association.