Familial Adenomatous Polyposis (FAP)-a premalignant clinical entity inherited as an autosomal dominant trait-is characterized by the development of hundreds to thousands of adenomatous polyps of the colorectum during the second and third decade of life. Approximately 80% of the FAP patients harbour truncating germ-line mutations in the APC tumor suppressor gene (Adenomatous Polyposis Coli). We tested 48 members from 9 families. Two novel truncating mutations were identified-2601delGA, R923X--and five already known mutations R564X, R876X, Q1045X, 3927-3931delAAAGA and D1822V were found. Our method for testing was PCR amplification from genomic DNA extracted from whole blood, followed by automated DNA sequencing.