Receptor Models (RM) identify pollution sources by solving a mass balance equation using measured chemical composition of samples either in combination with known source profiles or not. This approach has been extensively used in North America and South-eastern Asia mainly on Particulate Matter (PM). In Europe RM found wide acceptance and contributed to the identification of sources in support of remediation measures development. With the aim of harmonizing the activity on receptor modelling in Europe and supporting the implementation of Directive 2008/50/EC, a survey on the use of this methodology was carried out. In this study we discuss the sources of uncertainty in the input data, the common approaches to express uncertainties and their contribution deriving from critical steps. Improving comparability and reliability of receptor models can be achieved by performing intercomparison exercises. We describe the methodology used in an intercomparison exercise organised and evaluated by the JRC within the framework of the Forum for Air quality Modelling (FAIRMODE).JRC.H.2-Air and Climat