This work investigated the flux behavior of gas-sparging cross-flow ultrafiltration in flat-plate membrane module under various membrane inclinations and channel heights. The experiments were conducted using cellulose ester membrane (10,000 Da MWCO) and dextran T500 as the tested solute. The membrane inclination varies from 0 degrees (flow above membrane) to 180 degrees (flow below membrane). Experimental results show that the permeate flux increased significantly with increasing the gas addition in the narrow channel (2 mm height) no matter with the membrane inclination. In the large channel (10 mm height), the introduction of gas enhanced the permeate flux effectively as the membrane is installed at 90 degrees or 180 degrees inclination. The effect of gas slugs on disturbing the polarization layer depends on the position of gas slugs from the membrane surface. The dimensionless groups of filtrate resistance number and shear stress number were used to analyze the flux behavior, the filtrate resistance is minimum at 180 degrees inclination and gets maximum at 0 degrees inclination. Increasing gas velocity can reduce the filtrate resistance especially in the narrow channel. (c) 2006 Elsevier B.V. All rights reserved.