Congenital hypertrophy of the retinal pigment epithelium is a common eye sign in patients with familial adenomatous polyposis (FAP). FAP has autosomal dominant inheritance with virtually 100% risk of colonic malignancy in adult life. There may be other associated systemic abnormalities including extracolonic malignancy. Early detection of disease is desirable, but has in the past been reliant on regular endoscopic examination. The nature of congenital hypertrophy of the retinal pigment epithelium and its usefulness as a predictive marker of the disease are discussed.