The electrophoretic behavior of concentrated monodispersed, positively charged mercury drops is investigated theoretically. The present study extends previous analyses by considering arbitrary surface potentials, double-layer polarization, and the interaction between adjacent double layers. The coupled equations describing the spatial variations in the flow field, the electric field, and the concentration field are solved by a pseudo-spectral method. For a low surface potential phi(r), the mobility increases monotonically with kappaa; kappa and a are respectively the reciprocal Debye length and the radius of a mercury drop. For medium and high Or, the mobility curve has a reflection point, which arises from the interaction of adjacent double layers, for kappaa. Also, if phi(r) is high, the mobility curve may exhibit a local minimum as kappaa varies. This phenomenon is pronounced if the concentration of the dispersed phase is high. If the double layer is thick, the mobility increases with phi(r), and the reverse is true if it is thin. We show that the higher the concentration of the dispersed phase the smaller the mobility, and as kappaa becomes large the mobility approaches a constant value, which is independent of the concentration of the dispersed phase. The mobility of mercury drops is larger than that of the corresponding rigid particles. (C) 2003 Elsevier Science (USA). All rights reserved.