Background: In an effort to maintain procedure volumes and control consultation costs, many gastrointestinal endoscopists and primary care providers have implemented systems of open access endoscopy. In these systems, specialists in digestive diseases perform endoscopy without prior consultation. The purpose of this study is to determine if indications for upper endoscopic procedures requested in an open access system conform to national practice guidelines and to establish the yield of diagnostic information relevant for patient care in this system. Methods: Procedural indications and results for 3715 upper endoscopic procedures performed in an open access system were recorded in a computer database. The practice guideline “Appropriate Use of Gastrointestinal Endoscopy” (AUGE) of the American Society for Gastrointestinal Endoscopy was used to determine appropriateness of procedural indications. Results: Eighty-four percent of procedures were performed for indications listed in the AUGE, and 59% resulted in findings relevant to patient care. Specialists requested endoscopy more frequently for “approved” indications than did nonspecialists (p = .004) and more frequently had findings relevant to patient care (p < .001). Findings relevant to patient care are significantly more frequent for some indications listed in the AUGE compared to others (p < ..001). Conclusions: Adherence to practice guidelines can and does occur in an open access system. Specialists request endoscopy more frequently for appropriate indications compared to nonspecialists and have a higher yield of information relevant to patient care. Further refinement and better definition of some indications within the AUGE are needed to increase the clinical utility of this document.(Gastrointest Endosc 1997;46:15-20)