The results of the 25+ year Cancer Detection Center study, including 20,000 participants and 100,000+ patient-years experience, demonstrate the obviation of appearance of most lower bowel cancers associated with a program of proctosigmoidoscopy and adenomatous polyp removal. Once on a schedule of periodic examinations, study participants developed only a fraction of the anticipated number of rectal cancers; most of the cancers which did develop were detected while at an early stage and with involvement of only the mucosa. Not a single death from lower bowel cancer has occurred among active study participants or for 7+ years following the most recent examination at the Center.