Vitamin D deficiency was present in many US adolescents in this urban clinic-based sample. The prevalence was highest in African American teenagers and during winter, although the problem seems to be common across sex, season, and ethnicity.

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This individualized safer sex intervention may improve condom use and decrease the number of partners among adolescent girls who have had an STD. Studies with larger samples are needed to determine definitive intervention effects on recurrent STD in this high-risk population.

IntroductionDespite widespread public health campaigns, tobacco and alcohol continue to be used by a substantial proportion of adolescents. '-7 Tobacco and alcohol use appear to be occurring at younger ages, and they are correlated with one another, as well as with other problem behaviors.5-13 This clustering of problem behaviors is a particular concern with regard to adolescents who initiate tobacco and alcohol use during early adolescence.5'7"0 These data suggest that public health approaches may need to target other sources of influence on these behaviors.Adolescents