The action of relevant actors is of main importance for the ways in which market principles are implemented in welfare institutions and in how far the social and economic consequences of marketization lead to further institutional change in welfare states. According to the approach suggested here, actors do not simply act on the basis of economic rationality. Instead, they also act on the basis of ideas, and of established and sometimes changing power relations that may change as a consequence of marketization. Unintended social or economic consequences of marketization may lead to contra-trends and can be a driving force for further institutional change in welfare states. In this context, we aim to introduce and discuss new theoretical approaches and research about the role of actors and ideas for the introduction of market principles in care policies, the ways in which social actors experience the consequences of marketization, and consequences for the further development of the relevant welfare state institutions.