The present study was carried out to characterize the causative genetic mutation in a medium-sized Malaysian Chinese pedigree of three generations affected with familial adenomatous polyposis ( amilial adenomatous polyposis (FAP) is an autosomal dominant condition that is characterised by the development of hundreds to thousands of adenomatous polyps in the colon, beginning during the second or third decade of life. Untreated, colorectal cancer invariably develops and death from carcinoma is expected at a mean age of 42.