It is known that hydrophobic microfiltration membranes can be used for demulsification of oil-in-water (o/w) emulsion due to coalescence of oil droplets in membrane pores. This study demonstrates that a hydrophilic polymer membrane can be used for the demulsification of surfactant-stabilized water-in-oil (w/o) emulsions. The success of demulsification is dependent on the type of emulsions and membrane used. Membrane pore size and transmembrane pressure were found to affect demulsification efficiency (DM), while other factors, such as membrane thickness and initial water content have slight or almost no effect. A coalescence mechanism of the demulsification phenomenon is also discussed. The separation process is not based on sieving effects due to a difference in membrane pore size, but is determined by droplet interactions with membrane surface. (C) 2003 Elsevier B.V. All rights reserved.