FLADIS is an extendable software system integrated in a Geographical Information System (GIS) for displaying temporal and spatial distributions of concentrations of pollutants such as SO2, NO2, NO, particles, and O3 over whole areas. With the help of integrated statistical models, deposition of dust constituents can also be displayed over an area. FLADIS is designed for local authorities to fulfil the task of reporting. Furthermore it is a tool for combining and integrating information from measurements and models. Because the data for FLADIS have a geographical reference, a GIS is an ideal project environment and user interface for the system. FLADIS is integrated both in the GIS ArcView and MapInfo. It takes full advantage of the functionalities of the respective systems such as consistent georeferenced data storage and handling, analytical functions, and map generation and display. FLADIS consists of interpolation methods together with a dispersion or a statistical model. The interpolation is carried out by various methods such as, for example, Shepard, triangulation, and thin plate spline. The interpolation methods available can be expanded as needed through an interface for DLLs (dynamic link library). In the same manner, any available appropriate dispersion model or statistical model can be integrated into FLADIS. As output FLADIS calculates a weighted mean concentration for each grid point from the half-hourly or hourly results of the interpolation and the employed model.