Technical Abstract: Background: Adolescent girls and young women are at increased risk of vitamin D insufficiency, which can affect bone health and immune function. Subjects with HIV infection have alterations in vitamin D metabolism and an increased risk of osteopenia/osteoporosis. Objectives: The purpose of this study was to assess vitamin D status in the adolescents and young adults with HIV infection and in matched controls, and to determine if HIV infection was associated with an increased risk of vitamin D insufficiency. Design: Plasma 25(OH) vitamin D and vitamin D intake were measured in members of the Reaching for Excellence in Adolescent Health (REACH) cohort recruited in 12 US cities. Results: Study subjects were 14 - 23 y of age, 74% were female and 72% were black. Mean vitamin D intake from food was greater in HIV-positive subjects (295 ± 18 IU/d, n = 237) than in HIV-negative subjects (227 ± 26 IU/d, n = 121). Intake from food plus supplements was not significantly different between HIV-positive (400 ± 22 IU/d) and HIV-negative subjects (338 ± 33 IU/d). Mean plasma 25(OH) vitamin D in HIV-positive subjects (20.3 ± 1.1 nmol/L, n = 238) did not differ from that of HIV-negative subjects (19.3 ± 1.7 nmol/L, n = 121). The prevalence of vitamin D insufficiency (plasma 25(OH) vitamin D = 37.5 nmol/L) was 87% in the entire group and did not differ by HIV status. Low dietary intake, black race, body mass index, living in the northern US and winter/spring season were risk factors for vitamin D deficiency. Conclusion: The prevalence of vitamin D insufficiency in the REACH cohort was higher than expected considering their vitamin D intake and comparison to representative population data from black adolescents and young adults. It is possible that limited sun exposure among these disadvantaged, largely urban subjects may be the cause of this disparity.