Policy, defined broadly to include public policy as well as institutional or organizational policy, is useful for sustaining change in human development and its contexts and systems. The role for developmental psychopathology research in policy analysis and policy making is discussed. To assure that developmental psychopathology research is useful for policy (or practice) requires rigorous strategic thinking, commonly called "systems thinking". Systems thinking is described and its usefulness tested with a specific example of human development change--that of delinquency career crime prevention. Policy implications are then drawn from the example and generalized to broader human developmental change. (Contains 4 figures.)