This case study profiles one of 24 high schools that participated in a school-based, NIH-funded study to increase physical activity among high school girls. The case study school was one of 12 randomly assigned to the intervention group. The study intervention was based on the premise that a successful intervention is developed and tailored by teachers and staff to fit the context of their school. Intervention guidelines (Essential Elements) and the Coordinated School Health Program (CSHP) model were used to direct intervention activities for physical education, health education, school environment, school health services, faculty/staff health promotion, and family/community involvement. All girls at the case study school received the intervention. A team of school employees provided leadership to develop and implement the intervention in collaboration with a university project staff Data collected over a two-year period were used to describe changes that occurred in each CSHP area. Key changes were made in the school environment, curricula, policies, and practices. Qualitative measures showed girls more involved in physical activity. Quantitative measures taken in eighth grade, and repeated with the same set of girls in ninth grade, showed increases in both moderate-to-vigorous physical activity (p = <.01) and vigorous physical activity (p = .04). Other schools can use this case to modify components of the CSHP model to increase physical activity among high school girls. (J Sch Health. 2005;75(2):57-62)