A methodology that has received increasing attention in recent years is Integrated Assessment (IA). IA can loosely be defined as a multi- or interdisciplinary process of structuring various knowledge elements in such a manner that all relevant aspects of a problem are considered in their mutual coherence, for the benefit of decision-making. 

The notion of participation as a central element of Integrated Assessment is gaining wider recognition. This so-called Participatory Integrated Assessment (PIA) approach implies the engagement of non-scientific knowledge, values and preferences into the IA process through social discourse. This is considered to improve the quality of IA by giving access to practical knowledge and experience, and to a wider range of perspectives and options. Especially in the case of complex environmental issues, the involvement of non-scientific knowledge, values and preferences is considered to improve the decision-making process and also the quality of science. 

In recent years a wide variety of PIA methods and techniques has been developed, but also a strong renewed interest in PIA methods from previous decades is discernible. Often, many different methods are used and combined, but often without a clear argumentation why. 

This paper contains a literature survey on the PIA methodology. It addresses the methodological key-issues that should be considered in the design of a PIA approach. It argues that taking into account these key-issues can improve the design and application of a PIA approach. 

The first section of this paper deals with the concept of stakeholder participation. Different definitions of a stakeholder are compared, and the pros and cons of participation are described. The second section addresses different methodological key-issues that should be taken into account in the design of a PIA approach. These issues include the degree of participation, the role of scientists and the type of issue that is at stake. In the third section selected PIA approaches are discussed in relation to the methodological key-issues described in the second section. The last section of this paper wraps up.