In this work, asymmetric polyamide hollow fibre membranes having nominal molecular weight cut-off (NMWCO) of 10kDa, internal diameter of 1.5 (+/-0.1) mm, and thickness of 0.4(+/- 0.05) mm have been used to prepare oil-in-water emulsions. Pure isooctane (or isooctane containing naproxen methyl ester) as oil dispersed phase, ultrapure water (or 50 mmoll(-1)(50 mM) phosphate buffer pH 7.00) as continuous phase, and sodium dodecil sulphate (SDS) and polyvinyl alcohol (PVA) as emulsifier and stabiliser, respectively, were used.In order to achieve permeation of the apolar organic solvent, isooctane, through the hydrophilic ultrafiltration membrane it was necessary to pre-treat the membrane. The pre-treatment consisted in removing the polar internal liquid phase (water) and substituting it with the apolar solvent.Emulsion with narrow droplet size could be prepared, whose stability did not show any decrease for more than 20 days. Eighty-five percent of dispersed volume was contained in droplets with size of 1.87 (+/-0.58) mum. (C) 2003 Elsevier Science B.V. All rights reserved.