Terpolymers were synthesized by copolymerization of epichlorohydrin with ethylene oxide (EO) and allyl glycidyl ether. The terpolymers were crosslinked by sulfur curing. Conductivity of the crosslinked terpolymer compositions was investigated for application to an electrophotographic system. The composition containing 71 mol % EO units in the terpolymer gave high and stable conductivity over a wide range from low temperature and low humidity to high temperature and high humidity conditions. The conductivity of crosslinked terpolymer composition satisfied Ohm's law against the applied voltage from 10 to 1000 V, which is necessary for the electrophotographic system. The conductivity increased by the addition of a small amount of electrolyte. The staining ascribable to the migration of electrolyte was not observed, when 3 parts per hundred rubber by weight of octaclecyltrimethylammonium perchlorate was doped to the crosslinked terpolymer composition whose EO content in the terpolymer was 71 mol %. (c) 2005 Wiley Periodicals, Inc.