One unexpected point of convergence between the British and North American health care systems is the increased use of negotiated contracts to govern relationships between purchasers and providers. In Britain, the internal market reforms introduced a special regime of National Health Service (NHS) contracts; in the United States there has been a move from disorganization towards integration with the emergence of larger purchasing coalitions and provider organizations. While, in the past, US patients were simply billed for services or assigned claims to the provider, it is now common for payment to be made directly from purchaser to provider and for the terms of these transactions to be set out in contracts. This paper draws on the reading of contracts, interviews with contracting parties, and ongoing research on NHS contracting in Wales to compare contracting practice within the two systems. It examines how the very different environments of the public, hierarchically-regulated NHS and the private health care market of the US influence the detailed content of contract clauses. The analysis passes over similarities, different solutions to common problems, and fundamental differences of approach, before considering the possibilities for transfers of contracting 'technology'.