A simple model presented for cross-flow filtration of liquid suspensions was formulated on the premise that among the particles convected to the filter medium surface in cross-flow filtration, only a fraction of them become deposited. A criterion based on the interplay of the geometry of the cake-suspension interface and various forces acting on a particle as it moves toward the interface was established and an expression of the adhesion probability of impacting particles developed. The model was then formulated by incorporating the adhesion probability information together with conventional cake filtration theories. Through sample calculations, the model was found to display behavior consistent with the observed phenomena of cross-flow filtration and capable of representing experimental results.