This research uses data from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) to determine dietary and other factors associated with serum 25(OH)-Vitamin D concentration for 5,474 adults age 20 years and older. After multivariate adjustment, we found that serum 25(OH)-Vitamin D concentration was positively associated with diets high in fruits, vegetables, and lean meats, while diets high in processed foods and high-fat meats were inversely associated with vitamin D level. Serum 25(OH)-Vitamin D concentration was also signifi-cantly associated with age, gender, race/ethnicity, BMI, physical activity, supplementation, and the season of survey administration. Self-reported cardiovascular and kidney disease were significantly associated with serum 25 (OH)-Vitamin D concentration after adjustment for significant confounders.