Inclined dead-end ultrafiltration experiments were conducted for bovine serum albumin (BSA) solutions by using a specially-designed, unstirred batch filtration cell with the filtering surface of a square. Variations of the filtration rate were measured over time during filtration. Initially, short-term, severe flux decline occurred in the early period of filtration due to the formation of the thin filter cake over the membrane surface. Thereafter, the filtration resistance gradually increased over the long term of filtration. It was found from observations of the filter cake during filtration that the filter cake, which gradually slipped, grew on the lower side of the inclined membrane keeping its surface horizontal. Considering the decrease in the effective filtration area caused by the thick cake formed on the lower side of the membrane in addition to the formation of the thin filter cake over the membrane surface, a model was proposed to describe the dynamic behaviors of the filter cake during the long-term filtration and utilized to evaluate the variations of the filtration rate with time. On the basis of the cake accumulation model presented, the time evolutions of the filtration rate were evaluated for the different values of the inclined angle of the membrane, the solution pH, and the BSA concentration. It was shown that the calculations were in reasonable agreement with the experimental data. (C) 2012 Elsevier B.V. All rights reserved.