Unlike privatization, contracting out (or simply 'contracting') does not generally involve the sale of publicly owned assets. Yet it has been widely used as a mechanism for reform of public-sector service provision. Contracting introduces ex-ante competition-competition for the market through competitive tendering. This article examines both the theory and evidence of contracting by the public sector. It considers the theoretical conditions, such as contractual incompleteness and the ownership pf physical assets, which may impede efficient contracting. It also reviews the international evidence which suggests that savings in the order of 20 per cent are achievable, without sacrificing the quality of service provided. In the UK, savings of between £240m and £280m have been estimated for contracts let at the central government level. Substantial savings have also been generated by contracting at the local government level.