OBJECTIVE The objectives were to characterize the vitamin D status of black and white adolescents residing in the southeastern United States (latitude: approximately 33 degrees N) and to investigate relationships with adiposity. METHODS Plasma 25-hydroxyvitamin D levels were measured with liquid chromatography-tandem mass spectroscopy for 559 adolescents 14 to 18 years of age (45% black and 49% female). Fat tissues, physical activity, and cardiovascular fitness also were measured. RESULTS The overall prevalences of vitamin D insufficiency (<75 nmol/L) and deficiency (< or = 50 nmol/L) were 56.4% and 28.8%, respectively. Black versus white subjects had significantly lower plasma 25-hydroxyvitamin D levels in every season (winter, 35.9 + or - 2.5 vs 77.4 + or - 2.7 nmol/L; spring, 46.4 + or - 3.5 vs 101.3 + or - 3.5 nmol/L; summer, 50.7 + or - 4.0 vs 104.3 + or - 4.0 nmol/L; autumn, 54.4 + or - 4.0 vs 96.8 + or - 2.7 nmol/L). With adjustment for age, gender, race, season, height, and sexual maturation, there were significant inverse correlations between 25-hydroxyvitamin D levels and all adiposity measurements, including BMI percentile (P = .02), waist circumference (P < .01), total fat mass (P < .01), percentage of body fat (P < .01), visceral adipose tissue (P = .015), and subcutaneous abdominal adipose tissue (P = .039). There were significant positive associations between 25-hydroxyvitamin D levels and vigorous physical activity (P < .01) and cardiovascular fitness (P = .025). CONCLUSIONS Low vitamin D status is prevalent among adolescents living in a year-round sunny climate, particularly among black youths. The relationships between 25-hydroxyvitamin D levels, adiposity, physical activity, and fitness seem to be present in adolescence.