Some major factors of the melt spinning of high-density polyethylene (HDPE) and a liquid paraffin (LP) blend, which affect the water permeability of HDPE hollow-fiber membrane obtained therefrom, were investigated. The water permeability of the membrane was found to increase as the membrane thickness decreases and as the melt-flow-rate value of HDPE and the LP content of the blend increases. The dependence of the water permeability on the major factors is also discussed in connection with the morphology of the membrane. (C) 2000 John Wiley & Sons, Inc.