Familial adenomatous polyposis coli is an autosomal dominant hereditary form of colorectal cancer associated with mutations in the adenomatous polyposis coli (APC) gene on chromosome 5. The APC protein is thought to mediate the stability of beta-catenin in the WNT signaling transduction pathway ('wingless-type mouse mammary tumor virus integration site family member') in normal colonic epithelial cells, thereby indirectly regulating the expression of WNT target genes such as the c-myc-oncogene. APC gene mutations cause the development of multiple adenomatous polyps in the colorectum, which strongly predisposes gene carriers to colorectal cancer. Extracolonic manifestations, including gastric and duodenal polyps, osteomas, desmoids, epidermoid cysts, and retinal lesions, are commonly observed in patients with familial adenomatous polyposis. Detection of mutations in the APC gene allows genetic counselling and reliable identification of at-risk individuals.