In this paper, we use game theory to understand decisions to cooperate or to compete in the delivery of public health services. Health care is a quasi-public good that is often associated with altruistic behavior, yet it operates in an increasingly competitive environment. With mounting health care regulation and changes in privatization, altruistic arguments give way to more competitive rationales for market decisions. Profit and not-for-profit institutions must address widespread health care needs while balancing the needs of more lucrative markets against the needs of lesser ones. Recognizing the roles of cooperation and competition as motivators in the delivery of health care to the public is imperative. We explore two game theory models (Nash's Equilibrium and the Prisoner's Dilemma) and their related concepts of simultaneous interdependence and rationality to examine decision-making. Four hypothetical public health case studies are presented. We conclude that understanding game theory and the factors influencing decision-making allows potential competitors to make more efficient decisions, including decisions to cooperate or compete. As public health agencies move toward more collaborative models of service delivery, such understanding may help enhance efficient and effective service delivery. (Contains 6 tables.)