In 2002 the Dutch Ministry of the Interior enacted a new Local Government Act. The introduction of the new legislation was supported by a large-scale Innovation Program. The main objective of this institutional reform in local government was to improve the responsiveness and democratic accountability of municipalities by changing the role orientations and role behaviour of local councillors. The first question we address in this paper is whether these institutional reforms have indeed changed the relevant role orientations of the councillors. Despite widespread scepticism about the impact of institutional change, on the basis of surveys conducted before and after the reforms we found that the Dutch reforms may have been successful in changing some relevant role orientations of councillors. The second question in this paper is whether such possible changes in role orientations can be explained as the result of processes of (1) socialisation of councillors and (2) their selection.