Porous poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend hollow fiber membranes were prepared via thermally induced phase separation (TIPS) process. From the measurement of X-ray diffraction, the crystalline structure of PVDF hardly changed by blending with PMMA. When total polymer concentration was fixed at 30 wt%, water permeability of the blend membrane increased by increasing PMMA concentration. However, when PVDF concentration was fixed at 25 wt%, the trend of water permeability with the increase of PMMA concentration was contrary to the former case. Treating with acetone was applied to extract the PMMA from the obtained blend membranes. The extraction of PMMA was effective to increase water permeability. In addition,the extraction of PMMA brought about the improvement for the membrane elongation. The PVDF crystallinity was found to increase with the PMMA extraction due to the secondary crystallization. This was the reason for the elongation enhancement. (C) 2008 Elsevier B.V. All rights reserved.