International research on the social determinants of health has increasingly integrated a welfare state perspective, comparing and explaining the differing health outcomes of developed countries through reference to the concept of welfare state regimes. Although this is to be welcomed, to date the empirical research has been conducted without reference to much in the way of welfare state theories. In this paper, I situate welfare state regimes and health within the context of political economy theories of the development of the welfare state. Theoretical explanations of the initial emergence of post-war welfare state capitalism are described and the international variants (welfare state regimes) are outlined and compared. The crisis and reform of developed welfare states is examined and contextualised within the wider economic structural shifts from Fordism to post-Fordism. The emergence of new forms of welfare state regimes (post-Fordist workfare state regimes) is also described. Finally, these theories are related to what is already known from the empirical social epidemiology literature about differences in population health by welfare state regime.