Crossflow microfiltration experiments without intensification and with two-phase gas-liquid flow were performed on aqueous titanium dioxide dispersions using an alumina tubular membrane. The influence of gas flow velocity on flux was studied. The empirical model for steady state permeate flux and cake thickness prediction was developed. The results of experiments show positive effects of constant gas-liquid two-phase flow on the flux. It was found that there are no operating conditions at which air injection has no effect on the permeate flux. From analysis of the experimental results without gas flow, the empirical model based on Darcy's Law and on mass balance over a membrane module was derived. The model is based on dimensionless numbers regression of all basic operating conditions that influence permeate flux and cake thickness. The results showed good agreement between model prediction and experimental data with gas injection tested on the same apparatus. When the data from a different system (membrane type, membrane material) were taken, the agreement was not so good. (C) 2003 Elsevier B.V. All rights reserved.