The focus of this study was to empirically estimate the specific cake resistance (SCR) by the variation in shear intensity (G) in four laboratory-scale MBRs. The control reactor (MBR(0)) was operated with aeration only while other MBRs (MBR(150), MBR(300) and MBR(450)) were operated with aeration and mechanical mixing intensities of 150, 300 and 450 rpm, respectively. It was found that the SCR was strongly correlated (R(2) = 0.99) with the fouling rates in the MBRs. Moreover, the contribution of cake resistance (R(c)) to the total hydraulic resistance (R(t)) was predominant compared to the irreversible fouling resistance (R(f)). On this basis, the cake filtration model was selected as a predictive tool for membrane fouling. This model was modified by replacing the SCR with its empirical shear intensity relationship. The modified model can predict the fouling rate for a given shear intensity (G) within 80 and 250 s(-1) in a MBR system. (C) 2009 Elsevier Ltd. All rights reserved.