The authors analyzed a family in which three descendants presented with adenocarcinoma of the colon. In two of them the presence of colonic adenomatosis was observed. Another family member, a 13-year-old girl, presented with Turcot syndrome, that is, brain tumor associated with colonic adenomatosis. The nature of the hereditary transmission of Turcot syndrome is hence analyzed, discussing whether it happens through an autosomal recessive or a dominant gene. Undoubtedly the family has colonic adenomatosis, a disease considered of autosomal dominant transmission. Based on the clinical observation, the authors suggest that Turcot syndrome may be determined by an autosomal gene with a pleiotropic effect and variable expressivity.