Two cases of juvenile familiar polyposis (one 40-year-old male and his 14-year-old daughter) are presented. The girl presented intermittent rectal bleeding since the age of 10 with growth retardation and chronic anemia. The child was treated by colectomy with more than 100 juvenile polyps without adenomatous alterations being observed in the surgical specimen. Juvenile gastric polyps were also endoscopically observed. The father underwent sigmoidectomy for a adenomatous polyp of this localization. Later review of the surgical specimen demonstrated a juvenile polyp with zones of adenomatous alterations. The diagnostic difficulties of this rare entity and the therapeutic options available are discussed.