Objective: To describe the methodology of the Impact of a Preschool Obesity Prevention intervention enhanced with positive behavioral supports. Design: The social ecological model serves as the conceptual framework for this study, which has a within-and between-subjects design with an intervention group and a delayed intervention control group. This 3- year project will use formative methods to pretest materials in Year 1, collect data pre- and postintervention with a follow-up at 4 months in Years 2 and 3, and conduct summative and process evaluation in Year 3. Setting: Head Start centers in Southern and East-Central Mississippi counties. Participants: Three hundred parents with 3-year-old children enrolled in 9 Head Start centers (53 classrooms) and 75 Head Start teachers. Interventions: During Year 2, Hip Hop to Health Jr., Parent-Child Interaction Therapy, and Positive Behavior Interventions and Supports will be implemented. Main Outcome Measures: Primary outcomes include changes in parenting and teacher practices. Secondary outcomes include parent feeding styles as well as weight status and dietary intake. Variables will be measured using anthropometrics and validated surveys. Analysis: The primary analysis will be a multilevel 2 X 3 mixed ANOVA. (author abstract)