MOCAGE is the multiscale 3D Chemistry-Transport Model of Météo-France. It is run operationally for Air Quality, UV and dust forecasting, daily up to 96h. Meteorological forcings are provided by our NWP suites, ARPEGE and ALADIN. Forecasts are uploaded to the French platform Prév'Air (http://www.prevair.org). MOCAGE is also a research tool, with over 25 publications, and it is used in several European projects, like GEMS or AMMA. Last, a specific version will become operational soon for emergency response in support of our responsibilities of RSMC and VAAC. In operations, three domains (two-ways nesting) are used : globe (2°), Europe (0.5°) and France (0.1°). On the vertical, MOCAGE extends from surface up to 5 hPa (L47) with hybrid coordinates (□-P). A semi-lagrangian scheme is used for advection, while turbulent diffusion and convection are parameterized, using the Louis and Bechtold schemes respectively. The representation of dusts is based upon a sectional approach with 5 bins. Dust emissions are computed using the scheme of Marticorena and Bergametti over Saharan and Chinese deserts. Wet deposition, sedimentation and dry deposition are also taken into account to compute concentrations. Various diagnostics are available daily: mass concentrations on different altitude levels, column, emissions, AOD and separate sink terms. We present an overview of the system and its validation studies.