The entire gastrointestinal tract and bones were examined systematically in 24 patients (10 pedigrees) in whom familial polyposis coli was diagnosed. Polypoid lesions were observed in the stomach in as high as 68.2% of the cases, and in the duodenum in 90%. Abnormalities were noted in the skeleton in 50% and in the mandible in 81.3%. The authors emphasize the possibility that familial polyposis coli is substantially the same entity as Gardner's Syndrome.