Results (Phase I): 3121 patients had complete colonoscopy which revealed high rates of neoplasia: 37.5% had one or more neoplastic lesions; 10.5% had advanced neoplasia including 30 cases of invasive cancer (1%). There were 3.7% of patients with no lesions in the rectum or sigmoid colon who had advanced neoplasia elsewhere in the colon: 32% of all patients with advanced neoplasia would not be detected with an exam of the rectum or sigmoid colon (distal); 62% of patients with proximal advanced neoplasia would not be detected with an exam of the rectum and sigmoid colon. There were few serious complications (0.3%).