Neighborhood parks hold great potential as attractive and accessible settings to promote and enhance physical activity (PA) among racially/ethnically diverse low-income youth. However, little park-based intervention research has been conducted to explore how this potential might be realized. No previous park-level intervention has experimentally evaluated youth sports program fee waivers or intensive park outreach strategies to increase child enrollment and participation in park-based youth sports programs. The proposed research combines these promising intervention strategies into a single intervention and uses a gold-standard randomized controlled study design, and focuses on a low-income, racially/ethnically diverse sample at highest risk for developmental declines in physical activity. The proposed study evaluates the effects of a park-level intervention to increase moderate/vigorous physical activity (MVPA), and decrease sedentary time among low- income racially/ethnically diverse children ages 6-12 yrs. Neighborhood parks (n=24) will be randomized for a 2-year period to one of two experimental conditions: 1) Intensive Outreach and Youth Sports Program Fee Waiver; or 2) Comparison Condition: Current Outreach and Youth Sports Program Fee Structure. The intervention outreach and fee waiver components are expected to support parents to enroll their child in park- based youth sports programs by decreasing social/cultural and economic barriers to child enrollment and participation. The evaluation cohort will consist of 432 children ages 6-12 yrs who reside in one of the 24 park neighborhoods randomized to the experimental conditions. Measurements from individual children will be collected at baseline, 6, 12, and 24 months. Specific Aims of this research are: Specific Aim 1: To evaluate the effects of a park-level intervention on changes in child MVPA over 6, 12 and 24 months; Specific Aim 2: To evaluate the effects of a park-level interventions on changes in child sedentary behavior over 6, 12 and 24 months; Exploratory Aim 3: To evaluate the effects of a park-level interventions on changes in parent light activity and sedentary behavior over 6, 12 and 24 months. Hypothesis 1: Children who live in a neighborhood where the park is randomized to intensive park outreach and fee waiver will have larger increases in MVPA and decreases in sedentary behavior at 6, 12 and 24 months relative to children who live in a comparison neighborhood. Hypothesis 2: Parents of children who live in a neighborhood where the park is randomized to intensive park outreach and fee waiver will have larger increases in light PA and decreases in sedentary behavior at 6, 12 and 24 months relative to parents of children who live in a comparison neighborhood. IMPACT: The proposed research will provide evidence about the effectiveness of a park-based intervention that includes intensive park outreach and youth sports program fee waivers on changes in child physical activity in l...