Semi-crystalline poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully prepared utilizing a two step membrane preparation process. In the first step, precursory hollow fibers were formed from blends of PEEK and poly(ether imide) (PEI) by melt extrusion. In the second step, porous PEEK hollow fiber membranes were formed by selective decomposition and removal of the polyimide phase utilizing a primary amine reagent monoethanolamine (MEA). Quantitative removal of the PEI phase was confirmed by FT-IR spectra and gravity analysis. Porous PEEK hollow fiber membranes were successfully prepared from PEEK/PEI blends with PEEK/PEI blend ratios of 50/50, 40/60 and 30/70, respectively. The hollow fiber membrane morphology, thermal stability characteristics, gas and organic solvent transport properties were studied in detail for the hollow fiber membrane prepared from the PEEK/PEI blend with PEEK/PEI blend ratio of 50/50. The average pore size of the porous PEEK hollow fiber membranes prepared from the 50/50 blend is 11 urn. The permeance for pure oxygen is 2.26 x 10(-5) m(3) (STP) m(-2) s(-1) kPa(-1) (3000 GPU) and the permeance for nitrogen is 2.41 x 10(-5) m(3) (STP) m(-2) s(-1) kPa(-1) (3200 GPU). The ideal pure gas selectivity for oxygen/nitrogen is 0.938. Temperature and organic solvent permeation studies confirmed that the PEEK hollow fiber membranes prepared by the novel process can be operated at high temperatures and exhibit solvent resistance superior to most conventional commercial polymeric membranes. (C) 2010 Elsevier B.V. All rights reserved.