BACKGROUND: Despite the numerous physiological, psychological, and academic benefits of physical activity (PA), declines in PA levels among girls have been observed over the last decade. The purpose of this preliminary study was to assess the short-term changes pertaining to Girls on the Run and Girls on Track developmentally focused youth sport programs (DYS) on global self-esteem, body image, commitment to PA, and PA frequency. METHODS: This preliminary study employed a nonexperimental, one-group, pre- and postintervention study design using a 29-item paper-and-pencil assessment tool (n = 1034). RESULTS: Paired sample t-tests from pre- to postintervention revealed statistically significant differences in self-esteem (p <.001), body size satisfaction (p <.001), and vigorous PA frequency (p <.001). Stratification by the number of times participating in the intervention revealed the greatest changes at first participation followed with continued improvements in self-esteem (p =.013) and body size satisfaction (p <.001) for those participating in a second time. Age differences were also observed between participants ≤10 years old and 11-15 years; in that significant improvements in commitment to PA (p =.003) were observed for the older girls. CONCLUSIONS: Findings suggest DYS programs Girls on the Run and Girls on Track may produce beneficial changes in self-esteem, body size satisfaction, PA commitment, and PA frequency. Although the findings from the current report are preliminary, they suggest that DYS programs designed exclusively for girls may provide the necessary framework to promote PA to achieve the numerous associated benefits. © 2009, American School Health Association.