An easy operating, low-cost and fast method for determining the mean pore size of microfiltration (MF) membranes is offered by combining hydraulic resistance measurements with either electrical resistance measurements (ERM) or diffusional resistance measurements (DRM). ERM and DRM allow determination of the structural parameter epsilon/tau (2) which represents the ratio of membrane porosity to tortuosity factor squared. This parameter being determined, it is then possible to evaluate the mean pore radius from water flux measurements. The mean pore radius can be then determined from water flux measurements by taking into account the tortuosity of pores. This method was applied to MF ceramic membranes with two different pore sizes. Results show that epsilon/tau (2) values obtained by diffusion and ERM are very close. The mean pore radius determined from this method was found to be in very good agreement with that afforded by mercury intrusion porosimetry (MIP) for both membranes.