The lateral and vertical Gaussian plume dispersion parameters are estimated and compared with dispersion parameters determined for field tracer experiments conducted at 11 sites. The dispersion parameter schemes used in this analysis include Cramer's suggested for tall stack dispersion estimates, Draxler's, suggested for elevated and surface releases, and Pasquill's, suggested for interim use in dispersion estimates. These schemes estimate the dispersion parameters using on-site measurements of the vertical and lateral wind-velocity variances at the effective release height. Tables are presented summarizing the site-to-site variation in the performance of the schemes in estimating the derived dispersion parameters from the tracer experiments. The results suggest that the site-to-site variation in the performance of the schemes is in part related to the averaging time and sampling duration associated with the wind-velocity variances used in estimating the dispersion parameters.