The boundary effect oil the dynamic electrophoretic behavior of a charged entity is examined by considering a sphere in a spherical cavity. The present study extends previous analysis to the case of an arbitrary level of electrical potential where the effect of double-layer distortion call be significant. The governing equations are solved numerically based oil a pseudo-spectral method, which is found to be sufficient ill solving the corresponding electrophoresis problem when a static electric field is applied. The result of numerical simulation reveals that as the size of a cavity decreases. both the magnitude of the mobility and the inertial force acting oil a particle decrease accordingly. Also, while the distortion of the ionic Cloud should not be ignored, in general, when the Surface potential of a particle is high, its influence oil the magnitude and oil the phase angle of the mobility is alleviated by the presence of the cavity. (c) 2004 Elsevier Inc. All rights reserved.