Experiments were carried out at the Karlsruhe Nuclear Research Center to determine the atmospheric diffusion of pollutants. The influence on atmospheric diffusion by conditions specific to the site was investigated. For this purpose, tritiated water and two different halogenated hydrocarbons are emitted at heights of 60 and 100 m; their local concentration distribution is measured at ground level downwind of the source. The relevant meteorological data are measured at a 200-m-high tower. For evaluation of the measurements the diffusion is assumed to be a steady-state process. A twodimensional Gaussian distribution is used as the theoretical approximation of the concentrations. The dependence of the dispersion parameters σy and σz on the downwind distance is described by a power function. A least-squares fit is applied to calculate the horizontal and vertical dispersion parameters and the normalized diffusion factor from the measured wind velocity, emission rate, and concentration distribution. The errors in the calculated parameters are also determined. The dispersion parameters evaluated are assigned to stability classes by the measured standard deviation of the vertical wind direction.