Accountability as a relationship involves one individual or agency being held to answer for performance expected by some significant "other". Accountability relationships in the public sector have distinct and empirically observable phenomena associated with them. To understand accountability both historically and functionally people can view it as a sequence of problems facing rulers. These include problems related to: delegating tasks and establishing expectations; verifying the performance of those tasks; maintaining the responsiveness of accountable agents; assessing blame for accountable actions; sorting out responsibility among many agents; determining the "master"; and managing under conditions of multiple accountability systems. The chapter describes these problems in detail. It provides the following types of accountability relationships in democratic systems: legal accountability, political accountability, and professional accountability. Cultural settings of accountability permit someone or some group to be held accountable despite both blamelessness and the lack of formal answerability.