Abstract: Proposed is a flame-retardant heat-curable flowable epoxy resin composition suitable for use in case potting of film capacitors exhibiting very little settling of the particulate ingredients in storage and excellent impregnability in case potting as well as excellent flame retardancy, moisture resistance and tracking resistance of the composition after curing. The composition comprises, as a uniform blend:(a) 100 parts by weight of a bisphenol-based epoxy resin which is liquid at a temperature of working in case potting;(b) from 10 to 40 parts by weight of an alkyleneglycol diglycidyl ether or cycloalkyleneglycol diglycidyl ether;(c) from 80 to 120 parts by weight of a polycarboxylic acid anhydride;(d) from 4 to 20 parts by weight of a powder of red phosphorus; and(e) from 100 to 200 parts by weight of a powder of hydrated alumina which characteristically is a combination of (e1) from 80 to 95% by weight of a first powder of hydrated alumina having an average particle diameter in the range from 10 to 25 .mu.