This Guidance Document is addressed to those who are involved in risk assessment and management of chemicals called POPs (persistent organic pollutants) or PBTs (persistent and bio-accumulating toxics). It is about using multimedia models, i.e. generic evaluative models that can calculate overall environmental persistence (Pov) and potential for long-range transport (LTRP) covering multiple compartments such as air, water, sediment and soil: what models you can use to identify and characterize POPs/PBTs, what data to use, and how to use model calculations.