Therapeutic endoscopist specializing in endoscopic detection and resection of early gastrointestinal cancers. Renown for research in the prevalence and importance of flat colon polyps in the United States, development of new endoscopy technology, and outcome studies of a variety of endoscopic techniques. Significantly contributed to the recognition of the critical relationship of the easy to miss flat colon polyps and cancer. Pioneered the dissemination of methods to remove the flat polyps in the United States. Co-led development of the international guideline for the detection and management of flat dysplasia in patients with inflammatory bowel disease. Taught endoscopy by developing numerous self-instructional multimedia teaching modules that are widely used worldwide and received the American Society of Gastrointestinal Endoscopy Master Award for these efforts. More recent efforts are focused on developing new methods to teach endoscopy more efficiently and effectively. Current active efforts include developing simulation-based mastery learning with virtual coaching to learn endoscopy.