Background: Retinal pigment epithelium (RPE) lesions are predictive congenital phenotypic markers for familial adenomatous polyposis (FAP). This prospective screening study aims at assessing the incidence and significance of these lesions in FAP patients and their family members. Methods: Sixty-two members from three families including five patients with the diagnosis of FAP have been ophthalmologically surveyed. All RPE lesions were documented with fundus photography and fluorescein angiography was performed in 13 subjects. Sigmoidoscopy and/or radiological examination were performed annually in 9 family members with typical RPE lesions during 4 pears to allow early diagnosis of FAP. Results: Typical RPE lesions were present in five FAP patients and 15 family members. Telangiectatic dilatations in the retinal periphery with small dot-like hemorrhages were detected in 6 subjects from 3 families These lesions were particularly evident on fluorescein angiography. Annual colon analysis showed polyps in 3 out of 9 subjects who were positive for RPE lesions. Conclusion: RPE lesions are valuable as a clinical marker in predicting FAP. The co-existing peripheral vascular alterations which have not been reported before, are probably related to FAP.