Flexible sigmoidoscopy became available in 1976. To date, studies comparing it with rigid sigmoidoscopy support an increase of 2.5 to six times in the flexible sigmoidoscope's ability to detect polyps, and a two- to threefold increase in detection of colonic neoplasms in the same patients. This paper summarizes the current reported results of flexible sigmoidoscopy to date and describes the instrument and procedure as done at the UCLA Family Practice Residency Program. The flexible sigmoidoscope deserves evaluation for widespread primary care application.