Complexity of organization and resulting dynamic behavior are prominent attributes of the U.S. health care system.  These characteristics often compel analysts to deconstruct problems and take a piece-by-piece approach.  However, such a piecewise approach may miss subtle and powerful interactions within the larger health care system structure.  System dynamics methodology can be applied to identify and resolve issues arising in complex social systems such as health care. In a commercial managed care organization, a comprehensive system dynamics simulation model of the U.S. health care system helps users to make sense of systemic behavior and forecast key trends.