Public participation is increasingly considered as a plain part of the assessment and the management of a contaminated site. It is also perceived as a difficult and sometimes risky challenge. In Europe, to our knowledge, beside académie virtual experiments on "test groups", feedback and recommendations on the subject are scarce and dispersed. Following own expériences on real cases, INERiS and IRSN, in collaboration with the Cire Ile de France, hâve developed for ADEME a guide and a toolbox for organising public involvement in the assessment and the management of contaminated sites. The guide and the toolbox are intended for ail actors dealing with a contaminated site: public authorities, site owners, consultants, and représentatives of the public (organisations, elected représentatives, ...). They are available to ail on a dedicated website (www.comrisk.com). This article présents and discusses the outlines and the rationale of the guide and its related tools.