There is increasing interest among health policymakers, planners and donors in how corruption affects health care access and outcomes, and what can be done to combat corruption in the health sector. Efforts to explain the risk of abuse of entrusted power for private gain have examined the links between corruption and various aspects of management, financing and governance. Behavioural scientists and anthropologists also point to individual and social characteristics which influence the behaviour of government agents and clients. This article presents a comprehensive framework and a set of methodologies for describing and measuring how opportunities, pressures and rationalizations influence corruption in the health sector. The article discusses implications for intervention, and presents examples of how theory has been applied in research and practice. Challenges of tailoring anti-corruption strategies to particular contexts, and future directions for research, are addressed.