Background: After-school programs (ASPs, 3 pm to 6 pm) have been called upon to increase the amount of daily physical activity children accumulate and improve the nutritional quality of the snacks served. To this end, state and national physical activity and nutrition (PAaN) policies have been proposed. Frontline staff who directly interact with children on a daily basis are charged with the responsibility to meet policy goals. Without appropriate skills, staffers' ability to achieve such goals is limited. The gap between policies and improvements in PAaN must be bridged through professional development training. This article describes the development of an ASP staff professional development training program. Methods: A systematic review was performed to identify relevant theoretical perspectives, empirical evidence, and recommended best practices relating to promoting PAaN of children. Results: A comprehensive professional development framework was developed that incorporated the key elements identified from the review. These elements were distilled into 5 primary categories and conceptually referred to as the 5 "M"s: "mission"--clearly defined policy/standards for PAaN; "motivate"--providing choices, developmentally appropriate activities, feedback, and encouragement; "manage"--structuring and managing the environment for safety, routines, and discipline; "monitor"--ongoing evaluation of PAaN; and "maximize"--incorporating all former "M"s. Conclusions: The application of this training framework should lead to improved implementation and eventual achievement of policy goals for PAaN in ASPs. These competencies need to be developed in all ASPs if widespread improvements in PAaN within the ASP setting are to be realized. (Contains 2 tables and 1 figure.)