This paper focuses on the World Bank’s emerging experience with a promising application of performance-based contracts: Output-Based Aid (OBA) subsidies. OBA is the provision of subsidies for the delivery of and access to social or infrastructure services. Under OBA, subsidy payments are tied to measurable performing outputs, leaving the specific methods of achieving these outputs to the service provider’s discretion. While creating better risk allocation, more value for users and contracting agencies, and fewer opportunities for corruption than traditional methods, OBA schemes raise new procurement issues that need to be reconciled in order to achieve optimal results. An issue this paper explores is the tension between the need that contracts be “expenditure-based” with the “performance-based” nature of OBA subsidies.