Profile: Dr. Robertson is a Gastroenterologist with research interests both in the epidemiology of colorectal cancer (he is the Clinical Director of the Calcium and Vitamin D Polyp Prevention Study) and the utility of screening and surveillance for this disease. Although colonoscopy is increasingly performed, his research suggests that the degree of cancer prevention afforded may not be as great as suggested by earlier studies. He also recently received a VA Career Development Award to study the utility of fecal occult blood testing following a normal colonoscopy.