A flame retardant epoxy resin composition suitable for semiconductor encapsulation contains (A) a crystalline epoxy resin whose 30 wt % m-cresol solution has a viscosity of lower than 80 centipoise at 25° C., (B) a curing agent having at least two phenolic hydroxyl groups, and (C) silica. The composition optionally contains (D) an organopolysiloxane, (E) an organic phosphine oxide, (F) an amide group-containing release agent, and/or (G) a silane coupling agent. The cured composition achieves flame retardance rating UL-94 V-0 without a need for flame retardants and remains stable at high temperature.