The primary analyses performed on data collected during low-level tracer experiments conducted over metropolitan St. Louis, Missouri, are described. Values of dispersion parameters derived from the tracer data are related to readily derived or measured meteorological indices of turbulence. The results are graphically presented in terms of best-fit curves as functions of downwind distance and travel time. Comparisons are made with the results of previous diffusion experiments conducted over relatively uncomplicated terrain in open country. It is concluded that for low-level point sources the urban area affects cross-wind dispersion primarily by enhancing the initial size (i.e., close to the source) of the plume. (Author)