Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles. For twenty years he was the Associate Director of the Division of Gastroenterology at Cedars-Sinai Medical Center and an Associate Professor of Medicine, In Residence, at UCLA. At Cedars-Sinai he co-directed the Gastrointestinal Endoscopy Unit, taught physicians during their graduate and postgraduate training, and performed specialized, non-endoscopic, gastrointestinal testing. He carried out Public Health Service-sponsored (National Institutes of Health) clinical and basic research into mechanisms of the formation of gallstones and methods for the non-surgical treatment of gallstones. He is the author of 36 original research manuscripts and 24 book chapters. He is Co- Editor of the Webster's New World™ Medical Dictionary, Year 2000 First Edition. Dr. Marks presently directs an independent Gastrointestinal Diagnostic Unit where he continues to perform specialized tests for the diagnosis of gastrointestinal diseases.