A thermoplastic molding composition which comprises a blend of:(A) a copolymer having recurring units of a monoalkenyl aromatic monomer and recurring units of an .alpha.,.beta.-ethylenically unsaturated dicarboxylic anhydride N-substituted imide, and(B) a hydrogenated elastomeric block copolymer having at least one substantially completely hydrogenated diene polymer mid block and at least two monoalkenyl arene polymer end blocks in which at least a portion of the arene groups contained in the end blocks are substituted with at least one substituent selected from the group consisting of nitro, cyano and trifluoromethanesulfonyl.