This is a test in which a thin, black, flexible tube with a lighting system on the end is passed through the anus, into the rectum, in order to examine the large bowel or intestine, also called the colon. Colonoscopy is a very good test for examining the colon for polyps (warty growths that can turn into cancer), but it is not perfect. In fact, about 30% of polyps that are under 5 mm (about 1/5 of an inch) in size are missed during colonoscopy because they are hiding behind folds and bends in the colon. This research study is being done to determine if performing colonoscopy with a cap on the tip of the colonoscope will reduce the miss rate for polyps. A cap is a clear plastic hood that fits on the tip of the colonoscope and sticks out about 1/3 of an inch. During colonoscopy, the cap can be pressed against a fold or ridge in order to flatten it, so that the lining on the other side can be more easily seen. This may reduce the miss rate for colon polyps.