This chapter examines the general effects and effectiveness of choice of court agreements, focusing on contractual claims. An initial distinction is drawn between exclusive and non-exclusive jurisdiction agreements, while recognising that some agreements may combine features of both. The chapter then examines the rules governing the interpretation and validity of jurisdiction agreements, which may be both a matter of private international law and the applicable contract law. The question of the applicable law for a jurisdiction agreement is, however, complicated by the doctrine of severability and the uncertainty over whether a jurisdiction agreement should be characterised as substantive or procedural. The consequences of a jurisdiction agreement in different legal systems are then examined, looking at a range of direct and indirect effects which are determined by the private international law rules of each system. These include the major issues of whether a jurisdiction agreement effectively confers jurisdiction on the chosen court, and when an exclusive jurisdiction agreement is effective to derogate from the jurisdiction of any other court. Two further particularly contentious issues are then analysed – the issue of the validity and effectiveness of asymmetrical jurisdiction agreements, and the potential impact of jurisdiction agreements on third parties.