The medical profession is reputed to control decision-making in medical care to such an extent that one can speak of professional dominance. Yet West European health policies have radically changed the working conditions and incomes of doctors in many countries. Why have some governments been able to ‘socialize’ medicine? This article seeks to refute the view that the medical profession exercises a universal veto power. In contrast to scholars who explain medical influence in terms of singular characteristics of the medical profession or through the historical process of professionalization, this essay focuses on the properties of distinct political systems that make them vulnerable to medical influence. It argues that we have veto points within political systems and not veto groups within societies. By comparing the lobbying efforts of medical associations in Switzerland, France, and Sweden, the article analyses the role of political institutions in accounting for different patterns of medical association influence on health policy.