Familial adenomatous polyposis (FAP) is caused by mutations in the adenomatous polyposis coli (APC) gene, and different mutations may produce different clinical pictures. Most mutations occur in the 5' half of the gene, and mutations toward the 3' end are rare. The aim of this study was to document the phenotypes in a family with a truncating mutation at codons 1982-1983, one of the most 3' mutations on record. Colonic polyps in this family were much less numerous, and their growth was delayed compared with the classical FAP picture, and malignant degeneration occurred considerably later. Two individuals had sparse colonic but profuse gastric fundic gland polyposis. Gardner's syndrome stigmata were variable, and a desmoid tumor was recorded in 1 person.