A rectangular microchannel is the most popular shape to be widely used in microelectromechanical devices. However, analytical solutions of flow in this shape of microchannels are seldom reported because of its two-dimensional problem. Furthermore, microflows in microchannels are more difficult to describe. In this paper, we addressed analytically the problem of laminar electrokinetic slip flow in microchannels with a rectangular cross section subjected to a time-dependent pressure gradient and a time-dependent electric field. The analytical solution has been determined based on the Debye-Huckel approximation and its solution is useful to precisely control microflow with slip in rectangular cross-section microchannels. (C) 2003 American Institute of Physics.