Abstract: A process for preparing a porous film or sheet, which process comprises melt-forming a composition into a film or sheet and then stretching the thus-formed film or sheet at a temperature in the range of 30.degree. to 110.degree. C., said composition containing:(a) 30-90% by weight of a linear low-density polyethylene having a density not smaller than 0.910 g/cm.sup.3 and smaller than 0.940 g/cm.sup.3 ;(b) 10-70% by weight of an ethylene/.alpha.-olefin copolymer having a density not smaller than 0.860 g/cm.sup.3 and smaller than 0.910 g/cm.sup.3, a boiling n-hexane insolubles content not less than 10% by weight and a maximum peak temperature not lower than 100.degree. C. as measured according to a differential scanning calorimetry; and(c) 20-500 parts by weight of a filler based on 100 parts by weight of said resin components.