Abstract Introduction: Vitamin D deficiency is epidemiologically linked to prostate, breast and colon cancer. African American (AA) men have increased risk relative to European American (EA) men, but few studies evaluate vitamin D status in AA men. We evaluate the biological and environmental predictors of vitamin D deficiency in AA and EA men in Chicago, Illinois, a low ultraviolet radiation (UVR) environment. Methods: Blood samples were collected from 492 men, age 40–79, from urology clinics at three hospitals in Chicago, along with demographic and medical information, BMI, and skin melanin content using a portable narrow-band reflectometer. Vitamin D intake (dietary and supplemental) and UVR exposure were assessed using validated questionnaires. Results: Mean and median 25-OH D levels (normal: 30–80 ng/ml) were 17.2 and 16.0 ng/ml in AA men and 26.0 and 25.0 ng/ml in EA men, respectively (p < 0.01). Also, 93% of AA vs. 69.7% of EA men (OR = 1.33) were vitamin D deficient (P < 0.01). AA status (p = 0.04), age, and BMI (p < 0.01) were positively correlated with vitamin D deficiency, while vitamin D supplement use and sun exposure were negatively correlated (p < 0.05). Our multivariate analysis revealed that AA status, BMI, and lack of vitamin D supplementation were negatively associated with 25-OH D level (p < 0.05). Conclusion: Sunlight exposure, BMI and vitamin D supplementation are associated with vitamin D deficiency and represent modifiable risk factors. Race and sunlight exposure should be taken into account for recommended daily allowances for vitamin D intake. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):B54.