Recently, Castleman and Krickstein (1), Spratt and Ackerman (7), and others have cast considerable doubt on how frequently colonic polyps become malignant. As a result, excision is no longer advised whenever a polypoid growth of the colon is discovered, and differentiation between benign and malignant polypoid growths of the colon has become a challenge to the radiologist. Many x-ray and clinical signs have been noted, but no one of these is diagnostic. The purpose of this study was to determine whether the simultaneous evaluation of several variables, compared to only one variable, can improve diagnostic accuracy. Computer technics were used to facilitate the multiple calculations necessary. Material and Method The material consisted of 271 biopsy-proved polypoid growths of the colon, which had been demonstrated by the Welin air-contrast barium-enema method in Malmo, Sweden. Subsequent examinations of many of these growths permitted the determination of growth rates as measured by the doubling time (10)....