The concept of surface pore modification using colloidal silica was extended to polymeric membranes. Occlusion of surface pores of commercially available polysulfone, and polyvinylidene fluoride membranes were examined using silica particles suspended in a variety of dispersing media. Impregnation techniques previously proven effective with aluminum oxide membranes did not result in uniform and defect-free impregnation of the pores of the polymeric membranes studied.