Guidelines for the practice of endoscopy are developed by the American Society for Gastrointestinal Endoscopy by using evidence-based methodologies. A literature search is performed to identify relevant studies on the topic. Each study is then reviewed for both methodology and results. Controlled clinical trials are emphasized, but information is also obtained from other study designs and clinical reports. In the absence of data, expert opinion is considered. When appropriate, the guidelines are submitted to other professional organizations for review and endorsement. As new information becomes available, revision of these guidelines may be necessary. These guidelines are intended to apply equally to all who perform GI endoscopic procedures, regardless of specialty or location of service. Practice guidelines are meant to address general issues of endoscopic practice. By their nature, they cannot encompass all clinical situations. Clinical situations may justify a course of action at variance to these recommendations.