Epoxy resin compositions comprising (A) an epoxy resin of formula (1), (B) a curing agent based on a novolak type phenol resin and/or a triphenolalkane resin of formula (2), and (C) an inorganic filler are suitable for encapsulating semiconductor elements because they show good flow behavior upon casting and cure into less stressed products having improved mechanical strength, Tg, and moisture resistance. ##STR1## R.sup.1 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, OG is ##STR2## m is 0, 1 or 2, n is 1 or 2, and l is 0, 1, 2 or 3.