Industrial installations are only granted a license if model calculations have demonstrated that the emissions of the planned installation will not cause permitted levels of pollutants in ambient air to be exceeded. In Germany, the Technical Instructions on Air Quality Control (Technische Anleitung zur Reinhaltung der Luft, TA Luft) lay down requirements for such model calculations, and similar provisions are in place in other countries. However, it is the TA Luft that leads the way by prescribing a method referred to as Lagrange particle dispersion model. Unlike the Gaussian models commonly used elsewhere, this flexible modelling procedure produces realistic results even when buildings and uneven terrain influence flue gas dispersion. A computer programme which meets the TA Luft requirements has been developed on behalf of the Federal Environment Agency. It is available free of charge under the name of AUSTAL2000 and has proved its practical value. Modellers from abroad and new EU Member States apply AUSTAL2000 which is available as a full English version, too. Native Language Support allows a straightforward translation of the program to other languages.