One of the critical issues limiting the successful application of membrane filtration for treatment of drinking water and wastewater is typically membrane fouling of contaminants caused by pore clogging of the membrane and cake layer formation on the membrane surface during filtration. The overall objective of this paper is to systematically provide a fundamental understanding of the underlying mechanisms governing membrane fouling during membrane filtration, with particular emphasis on the pore clogging of the membrane in colloidal filtration such as microfiltration and ultrafiltration. A generalized characteristic form of four classical blocking filtration laws, which had been most extensively used in the analysis of the pore clogging of the membrane, was theoretically derived. The model accounts for the variations of both the porosity and specific surface area of the interior of membrane associated with the progress of deep bed filtration, on the basis of the Kozeny-Carman equation. Several new combined models have recently been developed to describe complicated filtration behaviors in which pore clogging of the membrane and growth of the filter cake occur in series or in parallel. In the future, the development of a more accurate model to explain the behavior of the irreversible pore clogging of the membrane, which will not fully recover by the simple physical backwashing and other periodic dynamic operations, will become increasingly important, in order to establish efficient membrane-based water treatment technologies.