Four sets of operational indicators of trafficking (adults and children for labour and sexual exploitation) resulting from a joint European Commission-ILO project. The Delphi methodology used to reach a consensus on these lists is presented in the brochure. This paper presents four lists of operational indicators of trafficking (respectively for adults and children in labour and sexual exploitation) which can be used to assess the situation of a potential victim of trafficking with respect to each of the six main elements of the definition of trafficking in human beings, as found in the Palermo Protocol : deceptive recruitment (including transfer and transport), coercive recruitment, recruitment by abuse of vulnerability, exploitation, coercion at destination and abuse of vulnerability at destination. These lists of indicators could become the reference tools for researchers and institutions in charge of data collection of trafficking in human beings in their country. This result was obtained through a participatory process among experts from the European Union who participated in a two-round survey. The Delphi methodology, described in detail in the brochure, allowed the experts to express twice their opinion and expertise, and to react on the opinions of the others. This research was implemented in 2008 in the context of a joint European Commission-ILO project, under the supervision of a steering committee composed of experts from the European Commission, International Labour Office, IOM, University of Tilburg, United Nations Office on Drugs and Crime (UNODC) and the European Union Agency for Fundamental Rights (FRA). More information about human trafficking on the website of ILO.