PURPOSE: Proband-reported family histories are widely used in epidemiological and genetic studies. The accuracy of these reports may have significant effects on the intended outcome, particularly in genetic studies. This study aims to determine the accuracy of proband-reported family history of myopia and to assess whether demographic or clinical factors are predictive of an accurate history. METHODS: In 2004 to 2005, the study recruited 120 myopic probands (< or = -0.50 D spherical equivalent in both eyes) aged 18 to 72 years and 358 nuclear family members residing within Victoria, Australia as part of the Genes in Myopia (GEM) family study. Data collection used an examiner-administered questionnaire with an ocular examination. Proband-reported family history of myopia was evaluated for agreement with ophthalmic examination results of family members. RESULTS: The statistical measures of accuracy used in this report were sensitivity, specificity, positive predictive value, and negative predictive value. Sensitivity varied from 85 to 98%, specificity from 84 to 96%, positive predictive value from 83 to 97%, and negative predictive value from 84 to 97%. Following multivariate analysis, an evaluation of demographic and clinical factors indicated that the highest predictive accuracy was obtained from proband reporting of their children [odds ratio (OR), 0.38; 95% confidence interval (CI), 0.15 to 0.94] whereas the most inaccurate reporting of a proband was when there was less-severe maternal myopia (per 0.50 D less myopic) (OR, 1.23; 95% CI, 1.06 to 1.43) or for increase in total education of the proband (per 1 year increase) (OR, 1.22; 95% CI, 1.04 to 1.42). CONCLUSIONS: Several variables influence the accuracy of obtaining a family history of myopia. A questionnaire-based approach alone will introduce some error into the study and this should be taken into account when designing and undertaking family-based epidemiological or genetic studies of myopia.