Background: The long-term success of child obesity prevention and control efforts depends not only on the efficacy of the approaches selected, but also on the strategies through which they are implemented and sustained. This study introduces the Multilevel Implementation Framework (MIF), a conceptual model of factors affecting the implementation of multilevel, multisector interventions, and describes its application to the evaluation of two of three state sites (CA and MA) participating in the Childhood Obesity Research Demonstration (CORD) project.Methods/Design: A convergent mixed-methods design is used to document intervention activities and identify determinants of implementation effectiveness at the CA-CORD and MA-CORD sites. Data will be collected from multiple sectors and at multiple levels of influence (e.g., delivery system, academic-community partnership, and coalition). Quantitative surveys will be administered to coalition members and staff in participating delivery systems. Qualitative, semistructured interviews will be conducted with project leaders and key informants at multiple levels (e.g., leaders and frontline staff) within each delivery system. Document analysis of project-related materials and in vivo observations of training sessions will occur on an ongoing basis. Specific constructs assessed will be informed by the MIF. Results will be shared with project leaders and key stakeholders for the purposes of improving processes and informing sustainability discussions and will be used to test and refine the MIF.Conclusions: Study findings will contribute to knowledge about how to coordinate and implement change strategies within and across sectors in ways that effectively engage diverse stakeholders, minimize policy resistance, and maximize desired intervention outcomes.