Germline mutation in APC gene induced development of familial adenomatous polyposis (FAP). The risk of developing specific manifestation of FAP is often correlated with the position of the inherited APC mutation. Patients with mutations localized in the largest exon 15 between codons 1286 and 1513 (mutation cluster region, MCR) have generally a worse prognosis with early onset of the disease. We found 6 FAP families with mutation at codon 1309 (3927_3931delAAAGA) in the cohort of 39 FAP Slovak families with rapid cancer progress. In addition, mutation in codon 1309 was detected in three family members, one of them with a very different phenotype. This oldest family member, aged 81, has persisted asymptomatic without clinical manifestations.