Background: Ocular surface epithelial dysplasia involves a spectrum of diseases ranging from only minor eye irritation to blindness and potentially death. Methods: A case-control study involving 60 patients with ocular surface epithelial dysplasia treated between 1972 and 1991 and 60 age- and sex-matched individuals was conducted to compare relative ultraviolet light exposures over their lifetimes. A standardized self-administered ultraviolet exposure questionnaire was used for assessment. Results: Risk factors identified include phenotypic features such as fair skin (odds ratio [OR], 5.4; 95% confidence interval [CI], 1.1,25.6), pale iris (OR, 1.8; 95%; CI, 0.9,3.8), and propensity to sunburn (OR, 3.8; 95% CI, 0.7,19.7), history of previous skin cancers removed (OR, 15; 95% CI, 2.0,113.6), and being outdoors more than 50% of time in the first 6 years of life white living 30 degrees or less from the equator (OR, 7.5; 95% CI, 1.8,30.6). Conclusion: These risk factors suggest that ocular surface epithelial dysplasia is an ultraviolet light-related disease.