Based on an analysis of the hydrodynamic forces acting on the suspended colloids, a new model is presented for filter cake buildup and growth under crossflow filtration conditions. It is shown that the rate of cake buildup is explicitly dependent on the particle size distribution in the suspension, the rheology of the suspension and the suspension shear rate. The model shows that the cake formed is inhomogeneous, with progressively smaller particles being deposited on the cake surface as filtration proceeds. An equilibrium cake thickness and filtration rate are achieved when there are no particles in the suspension that are small enough to adhere to the cake surface.