Several kinds of powders were dispersed into air by use of a mixer type or a nozzle-jet type dry disperser and the size distributions of the dispersed aerosol particles were measured. In the data analysis, a newly defined dispersion efficiency was introduced in order to represent the dispersion state of aerosol particles, independently of the sort of tested powders. On the other hand, the adhesive characteristic value representing the inter-particle adhesive force was obtained through a particle re-entrainment test developed in our laboratory. The data expressed by use of the dispersion efficiency and the adhesive characteristic value made it possible to evaluate quantitatively the disperser performance for different kinds of powders. It was found that the dispersion efficiency was well correlated with the adhesive characteristic value as far as the mass flow ratio between particles and air was kept constant. Therefore, the dispersion efficiency of any powder can be estimated by the particle re-entrainment test.