Ophthalmological examinations were performed in 49 people (43 patients) from 24 families affected by familial adenomatous polyposis (FAP). No features of congenital hypertrophy of the retinal pigmented epithelium (CHRPE) were noted in six first-degree relatives without colonic polyps. Patients with Gardner's syndrome exhibited CHRPE more frequently than those without exostosis or desmoid tumour (91 per cent versus 45 per cent). In addition the prevalence of CHRPE was slightly higher in the patients with gastric or duodenal polyps (68 per cent compared with 50 per cent) in those who had a normal gastroduodenal examination. There were 11 families in which two or more patients underwent ophthalmological examinations. In five of these 11 families, all 12 patients were negative for CHRPE. In four of the remaining six families, all 11 patients had CHRPE. CHRPE is one of the pleiotropy of FAP and ophthalmological examination is an important screening test for the family of patients with CHRPE associated with FAP.