This chapter explores what conditions Integrated Assessment Models (IAMs) should meet in order to be of better use in support of participatory Integrated Assessment processes. It discusses the epistemological and societal characteristics of the problem and the implications with regard to what management strategy is appropriate to tackle the climate problem. The chapter explains what IAMs are, how IAMs emerged, and how IAMs have been used in the process by which the risks of anthropogenic climate change. It also discusses several trends in IA, including the participatory challenge, and how the IAM community has responded to these trends and challenges. The chapter presents some preliminary empirical results from IAM-use in IA focus groups obtained within the European Urban LifestYles, SuStainability and Integrated Environmental Assessment (ULYSSES) project. The ULYSSES project, funded by the European Commission has been designing and testing a procedure to allow informed citizens to express their judgments on climate policy.