A case-control study was set up to assess the risk of eye melanoma in relation to the number and type of cutaneous melanocytic naevi and pigmented lesions of the iris. Cases comprised 211 unselected ocular melanoma patients attending the Ocular Oncology Clinic at Moorfields Eye Hospital, London, during November 1990 to October 1991 and diagnosed after August 1986. Hospital and general practice controls (416) were recruited in the North East Thames Region of the UK. Cutaneous naevi greater than or equal to 2 mm in diameter were counted on the skin. Clinically atypical and congenital naevi were recorded separately. Pigmented lesions of the iris were counted. The relative risk for ocular melanoma increased with numbers of atypical naevi and numbers of common naevi. Ten percent of cases but 3% of controls had at least 100 naevi of 2 mm or greater diameter. Seven percent of cases and 0.4% of controls had 4 or more atypical naevi. Pigmented lesions of the iris were significantly more common in cases than controls. Nine percent of cases had the Atypical Mole syndrome (AMS) phenotype compared with 1% of controls. Six cases had concurrent cutaneous melanoma primaries. We conclude that atypical and iris naevi are important risk factors for eye melanoma and that patients with eye melanoma are at increased risk of cutaneous melanoma. Dermatological examination for the AMS phenotype and cutaneous melanoma should be recommended in eye melanoma patients with large numbers of pigmented lesions of the skin or family history of melanoma.