In the present paper the flow of a Bingham fluid between two parallel porous walls is studied. One of the walls moves with constant velocity parallel to the other, which is fixed, while a longitudinal pressure gradient exists, as well as a transverse flow field due the porosity of the walls. An exact analytical solution is given for the u-velocity field, which has four different forms depending on the values of the three dimensionless parameters, which are the Bingham, Couette and Reynolds numbers. (C) 2007 Elsevier B.V All rights reserved.