Collision and electrostatic dispersion rates of airborne submicrometer TiO(2) agglomerates were measured and compared with the classical collision theory for spheres as well as with models accounting for the agglomerate structure in terms of the fractal dimension and electrostatic effects such as Coulomb and van der Waals interactions. According to the authors' knowledge, this is the first time that the agglomerate fractal dimension and electrostatic effects have been considered simultaneously in determining the collision frequency function of agglomerates. The observed enhancement in the collision frequency of agglomerates was found mainly to be a result of electrostatic particle interactions. Nonspherical particle shape has only a comparatively small influence on the collision probability, on the order of 10-20%. Electrostatic dispersion coefficients of agglomerates were found to be similar to those of spheres. Copyright 2001 Academic Press.