Context: Vitamin D deficiency is not adequately evaluated in older men. Objective: The aim of the study was to determine the prevalence of vitamin D deficiency and identify risk factors for its occurrence. Design and Setting: We conducted a cross-sectional evaluation of 1606 older men in the general community who were enrolled in the Osteoporotic Fractures in Men Study. Participants: A randomly selected subcohort of a large population of men from six U.S. communities participated in the study. Main Outcome Measures: Serum concentrations of 25-hydroxyvitamin D2 [25(OH)D2] and 25(OH)D3 were measured using mass spectrometry. Results: Deficiency [25(OH)D <20 ng/ml] was present in 26%, and insufficiency (<30 ng/ml) was present in 72%. Deficiency was particularly common among men during the winter and spring (especially in the northern communities) and in the oldest and more obese men. For instance, in Caucasian men in winter or spring who were >80yrold, did not engage in lawn/garden work, and had a body mass index greater than 25 kg/m2 and vitamin D intake below 400 IU/d, the prevalence of vitamin D deficiency was 86%. 25(OH)D2 levels were present in a small fraction of men and accounted for a low proportion of total 25(OH)D levels. The use of vitamin D supplements was reported by 58% of men, but supplement use had a small effect on total 25(OH)D levels and, despite supplement use, low levels remained frequent. Conclusions: Vitamin D deficiency is common in older men and is especially prevalent in obese, sedentary men living at higher latitudes. Use of vitamin D supplements at levels reported here did not result in adequate vitamin D nutrition. Copyright © 2009 by The Endocrine Society.