Klaus Petersen's research focuses on the history and politics of the welfare state with particular emphasis on Denmark and the Nordic countries. He is recognised as one of the world's leading experts on the Danish and Nordic welfare models and has been pivotal in renewing research approaches to Danish and Nordic welfare history. His approach emphasises integration of political and cultural history, and linking historical and social science methodologies. Klaus Petersen took part in establishing the Danish Centre for Welfare Studies as an internationally recognised center with a unique interdisciplinary profile.