A mean-field theory of electronic and atomic dispersive hopping and/or multiple trapping transport in disordered solids is presented. The theory is based on a set of microscopic Markovian transport equations which are solved for the averaged dc and ac mobility by means of a two-site effective medium approximation. The averaged transient current is obtained by solving the macroscopic equation for the carrier profile with the frequency-dependent mobility as input. Results are shown for the case of hopping among impurities with spatial disorder. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.