It is the aim of this 1-day course to provide the theoretical background to odour dispersion modelling in order to permit delegates to: use odour models with confidence; select appropriate input data; interpret the output data and be aware of the limitations in the modeling exercise. It will start by considering basic aspects of meteorological conditions which play an important role in plume spreading. These aspects together with source emissions data allow the formulation of realistic dispersion models. Such models can be described either by a complex set of equations or by a single algebraic equation depending on the required output from the model, the speed of response and the costs involved. The most common commercial dispersion models are usually based on Gaussian assumptions and on a number of empirical parameters that facilitate a rapid response and low cost. However, as computer processing technology advances, tools based on a CFD approach are becoming more commonplace. But whatever the dispersion model is used, the most important thing is to understand its fundamentals in order to fully exploit its potential and also to be aware of its limitations in order to interpret accurately the output.