A similarity solution is presented for the convective-diffusion equation governing the steady-state concentration—polarization boundary layer in crossflow microfiltration of the particles, under conditions where a thin stagnant layer of particles deposited on the microporous membrane surface provides the controlling resistance to filtration. The analysis employs concentration-dependent shear viscosities and shear-induced hydrodynamic diffusivities based on empirical correlations for suspensions of rigid spheres. The resulting permeate flux is v w( x) = τ w( a 4/3 x) 1 3 ν t- w/μ 0, where x is filter entrance, τ w is the wall shear stress exerted on the boundary layer by the tangential flow of bulk suspension through the filter channel, a is the particle radius, and μ 0 is the characteristic viscosity. The dimensionless permeate flux, ν − w (φ b), depends only on the particle volume fraction in the bulk suspension, φ b, and is given by ν − w = 0.0581φ b − 1 3 when the suspension is dilute (φ b < 0.10). The results for the permeate flux and for the concentration and velocity profiles show that the approximate solution of Davis and Leighton [ Chem. Engng Sci. 42, 275–281 (1987)] and Romero and Davis [ J. Membrane Sci. 39, 157–185 (1988)], which neglects axial convection in the differential particle mass balance but retains it when integrating across the entire boundary layer, is exact in the dilute limit and accurate to within a few percent for nondilute suspensions. The solution may easily be extended to other suspensions having different dependencies of viscosity and diffusivity on concentration.