Many government bodies relate to each other through contracts: government departments and agencies; government departments and the Treasury; National Health Service (NHS) purchasers and NHS Trusts. These 'internal contracts' are not, in general, regulated or enforced by the law. This book explores the practical problems encountered by the parties to internal contracts, drawing on evidence from an empirical case study of NHS contracts. It uncovers difficulties in defining the parties' roles; in maintaining good working relationships; and in securing compliance with contractual terms. It then examines the possibility of solving these problems through law. Some commentators, particularly public lawyers, have condemned the law's failure to keep pace with the rise of 'government by contract', but few have made specific proposals for reform. The book develops an original public law analysis of internal contracts, interpreting them as mechanisms of accountability from service providers to purchasers. It proposes norms which would help the parties to use their contracts as fair and effective mechanisms of accountability. It also suggests reforms to the institutional framework for internal contracts. The book will be of interest not only to academics working in the fields of law and public administration, but to policy-makers concerned with the contractualisation of public services. It also has wider implications for the regulation of other types of government contract, and should stimulate debate among public lawyers on the neglected issue of 'government by contract'.