The objective of this paper is to demonstrate that membrane performance (flux, rejection, and permeate particle size distribution as a function of time) can be influenced by modifying the membrane pore side characteristics. Poly(ethylene teraphthalate) (PET) track-etched (T-E) membranes with nominal pores sizes ranging from 0.2 to 10 mu m were uniaxially stretched to increase the major axis, aspect ratio, pore area, and porosity while decreasing the minor axis. Permeation results for pure water feed as well as separate feed suspensions of spherical particles and irregular-shaped particles showed that flux can be increased and flux decline decreased by stretching membranes. Additionally, rejection of both irregular-shaped and spherical particles was increased by stretching membranes. (c) 2006 Elsevier B.V. All rights reserved.