"The book addresses a very timely question. Many policy making areas demand more systematic and valid knowledge input but, at the same time, knowledge and expertise are more and more contested. There is a competition of knowledge claims as well as a general insecurity about the quality criteria for knowledge in policy contexts. The book analyses the relationship between policy arenas and the characteristics of expertise in the context of environmental regulation; it offers many new insights and innovative thoughts about the role and function of expertise in complex decision making arenas." - Prof. Dr. Dr. h.c. Ortwin Renn, Chair of Environmental Sociology at the University of Stuttgart. The analysis of the book contributes to the theory of the expansion of expertise, and comments on the recent debate on the so-called normative theory of expertise by Collins and Evans. The book is targeted at researchers and practitioners of citizen participation, risk management, technology assessment and foresight and S&T policy.