This article presents a discussion of the relevance of the U.S. experience in general, and health maintenance organizations in particular, to the reforms advocated by the current Conservative government in the general practitioner services of the British National Health Service. The author analyzes empirical information relevant to the assumptions made by the Conservative reformers that (1) the HMO type of practice is better able to respond to people's needs than are current general practitioner arrangements; (2) entrepreneurship in medicine is good for patients; (3) market-based primary care is more efficient than the nonmarket system in the United Kingdom; and (4) the expansion and strengthening of the private sector is an efficient and equitable means of encouraging competition and raising revenues. All of these assumptions are questioned.