An epidemiologic study is proposed which will determine possible risk factors for colorectal adenomatous polyps. These lesions are generally accepted as precursor lesions for most cases of colorectal carcinoma, though very little is known about possible etiologic factors. A case control strategy will be utilized which will compare patients found to having polyps at colonscopic examination with colonoscoped patients found to have normal bowel mucosa. Efforts will be made to carefully characterize the polyps with regard to degree of atypia, size and number. The subjects of the study will be drawn from two medical centers, Presbyterian Hospital of the City of New York and the Dartmount-Hitchcock Medical Center in New Hampshire; the expected accrual over 2 years numbers 480 adenomatous polyp patients, 200 cancer patients and 400 colonoscoped controls. Because of potential bias in the control group, a second control group is proposed which would consist of 480 neighborhood controls selected by random digit dailing (RDD) and matched to polyp cases for age, gender and telephone exchange. Trained interviewers will administer a structured questionnaire by telephone to all participants which will emphasize risk factors previously associated with colon cancer or polyps, such as cigarette smoking, alcohol consumption, prior appendectomy or cholecystectomy, parity, steroid hormone use, asbestos exposure, laxative use and family history of colon cancer. A food frequency questionnaire will be used to characterize invividuals as to dietary intake of fat, meat, fibre, vitamin A and carotene; demographic variables will be collected as well. The goals of this investigation are to determine possible associations between hypothesized risk factors and colorectal polyps, and to explore these relationships in successive stages of colorectal neoplasia. This information will hopefully lead to future strategies for the prevention of colorectal polyps and carcinoma.