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ObjectiveTo assess the inter-method reliability of the Ovarian Cancer in Alberta (OVAL) survey developed to estimate adult vitamin D exposure from sun and diet for every tenth year, against the longer Geraldton Skin Cancer Prevention Survey (the assumed ‘gold standard’). We also estimated total vitamin D exposure using the OVAL survey.DesignA randomized crossover design to assess the inter-method reliability of sun exposure (OVAL v. Geraldton survey), using intra-class correlation and estimated total vitamin D exposure from sun and diet.SettingCalgary, Alberta, Canada.SubjectsRandomly selected women (n 90) aged 40–79 years.ResultsThe average lifetime sun exposure of 13 913 h (average 411 h/year) from the Geraldton survey was not significantly different from the 13 034 h (average 385 h/year) from the OVAL survey for periods with sufficient UV radiation to stimulate vitamin D production. The intra-class correlation coefficient for average lifetime sun exposure was 0·77 (95 % CI 0·69, 0·86); the annual average was 0·60 (95 % CI 0·47, 0·74). Estimated vitamin D from diet and supplements increased with age.ConclusionsOur OVAL survey reliably estimated adult sun exposure relative to the Geraldton survey, suggesting that assessing sun exposure every tenth year is a reliable and efficient method for estimating sun contributions to lifetime vitamin D exposure. [ABSTRACT FROM AUTHOR]