Brief Summary: RATIONALE: Collecting and storing samples of tissue, blood, and other body fluids to test in the laboratory and gathering information about health and lifestyle from participants may help doctors learn more about cancer risk factors. PURPOSE: This clinical trial is looking at biological, genetic, and lifestyle risk factors for developing colorectal adenomas or polyps in participants undergoing colonoscopy.

Detailed Description: OBJECTIVES: * To recruit 7,000 participants who are planning to undergo colonoscopy. * To collect questionnaires and medical records from these participants. * To collect biological samples, including urine, blood, buccal cells and/or saliva, rectal tissue, and colorectal polyps from these participants. * To evaluate risk factors and other differences between participants found to have polyps and those who do not have polyps. OUTLINE: Participants undergo screening colonoscopy and removal of any polyps. Within 1 month of colonoscopy, participants undergo a 30-minute telephone interview and/or complete a mail survey to provide information on lifestyle and medical history that may be related to colorectal polyp risk. Participants who undergo removal of polyps during their colonoscopy also complete a 20-minute survey at their 3-year follow-up colonoscopy. Participants' medical records may also be reviewed. Blood samples are collected at the time of colonoscopy. Some participants may also provide blood samples 1-2 weeks prior to colonoscopy. Tissue from the bisected portions of colorectal polyps \> 5 mm in size that are removed during colonoscopy is also obtained. Some participants may also undergo normal colorectal tissue sample and saliva sample collection at the time of colonoscopy and urine sample collection 2 days prior to, during, and/or 8 weeks after colonoscopy. Tissue samples may be stored for future genetic studies to evaluate genetic factors that may cause or be related to colon polyps or colorectal cancer.