A computer model using actual meteorological data is developed to simulate the effects of wind shear on an instantaneous pollutant puff. The effect of wind shear on dispersion is obtained by subdividing, during the nocturnal phase, the previous daytime pollutant mixed layer into 300 m layers. Each layer is tracked as a separate trajectory. Vertical mixing is resumed during the next daytime phase. Further subdivisions occur each nocturnal phase. The computer simulation of puff growth as a result of shear confirmed the proportionality of puff spread to geostrophic wind speed during homogeneous conditions as derived by Taylor (1982). Both Taylor's and the computer simulation results are consistent with published experimental long-range dispersion data representative of average conditions. Abstract A computer model using actual meteorological data is developed to simulate the effects of wind shear on an instantaneous pollutant puff. The effect of wind shear on dispersion is obtained by subdividing, during the nocturnal phase, the previous daytime pollutant mixed layer into 300 m layers. Each layer is tracked as a separate trajectory. Vertical mixing is resumed during the next daytime phase. Further subdivisions occur each nocturnal phase. The computer simulation of puff growth as a result of shear confirmed the proportionality of puff spread to geostrophic wind speed during homogeneous conditions as derived by Taylor (1982). Both Taylor's and the computer simulation results are consistent with published experimental long-range dispersion data representative of average conditions.