The electrostatic dispersion of polydisperse aerosol particles carrying unipolar charge was studied theoretically and experimentally. The time-dependent behavior of polydisperse aerosols due to electrostatic dispersion in stationary air and a laminar pipe flow is evaluated by numerically integrating the "birth-death" equations for various conditions. The results are compared with those obtained from the well-known Wilson''s equation, which is derived for a monodisperse aerosol having uniform charge quantity in stationary air. The effects of particle size distribution, particle charge distribution, image force and flow conditions of aerosols on the aerosol behavior were studied. It was found that Wilson''s equation can roughly estimate the decrease in number concentration of polydisperse aerosols, if mean electrical mobility and geometric mean radius are used to take account of the effect of polydispersity of both charge and size. Some of the calculated results were in good agreement with the experimental results obtained in a closed chamber and in a laminar pipe flow.