PROJECT SUMMARY/ABSTRACT Children from low-income families are more than twice as likely to become obese than those from higher- income households, which places them at increased risk for obesity-related chronic diseases throughout their adult lives. Family-based pediatric obesity interventions, particularly those designed for low-income populations, are increasingly delivered in children’s homes. Home visitation has a number of potential advantages that could enhance weight loss outcomes relative to delivering treatment in traditional medical and academic settings. By eliminating the need for transportation and childcare, home visitation may make treatment more accessible for low-income families, resulting in a higher dosage of intervention received. Home visitation allows intervention staff to directly observe and address risk factors in the home environment, potentially enabling them to provide more tailored and potent treatment recommendations. Caregivers may also be more likely to apply healthy changes in their household when they learn and rehearse new skills in the environment where they are to be implemented. Research to date has consistently found that home-based interventions are more effective than low-intensity comparison conditions such as wait-list controls, health education, and usual medical care. Yet, as the home visitation treatment modality has been confounded with intervention dosage, intensity, and content in prior studies, there is a lack of empirical evidence to support its use. The goal of this project is to systematically evaluate the incremental weight loss benefit and cost- effectiveness of delivering standard family-based treatment for pediatric overweight/obesity in the home setting vs. traditional medical settings. In a randomized controlled trial involving low-income households, 266 children ages 6-11 years will be allocated to 12 months of family-based treatment delivered either in their home or at an urban academic medical center. Both arms will receive the same intervention content and dosage, and differ only in the location of in-person treatment sessions. Aim 1 is to test the hypothesis that home-based treatment produces a greater reduction in child adiposity, reflected in 12-month change in BMI z-score. Aim 2 is to compare the cost-effectiveness of home-based treatment to medical center-based treatment, and calculate the added cost of the incremental weight loss benefit associated with home visitation. These data will inform efforts to disseminate home-based interventions for low-income populations by public health agencies and third-party payers. Aim 3 is to explore specific mechanisms through which home visitation may improve weight loss outcomes. The results of this trial will have a strong impact on the design of future pediatric overweight/obesity interventions, as virtually any program could be adapted for delivery in the home setting.