Comparative histories of health system development have been variously influenced by the theoretical approaches of historical institutionalism, political pluralism, and labor mobilization. Britain and the United States have figured significantly in this literature because of their very different trajectories. This article explores the implications of recent research on hospital history in the two countries for existing historiographies, particularly the coming of the National Health Service in Britain. It argues that the two hospital systems initially developed in broadly similar ways, despite the very different outcomes in the 1940s. Thus, applying the conceptual tools used to explain the U.S. trajectory can deepen appreciation of events in Britain. Attention focuses particularly on working-class hospital contributory schemes and their implications for finance, governance, and participation; these are then compared with Blue Cross and U.S. hospital prepayment. While acknowledging the importance of path dependence in shaping attitudes of British bureaucrats toward these schemes, analysis emphasizes their failure in pressure group politics, in contrast to the United States. In both countries labor was also crucial, in the United States sustaining employment-based prepayment and in Britain broadly supporting system reform.