An all-aromatic thermosetting copolyester has been prepared using hydroquinone, hydroxy-benzoic acid, isophthalic acid, trimesic acid, and/or 1,3,5-triacetoxybenzene as key building blocks. The preparation and characterization of these materials are described. Cured resins based on these structures exhibit thermal stabilities in nitrogen to 450 degrees C, glass transition temperatures up to 240 degrees C, and moisture pickups elf only 0.3 wt%. An important feature of these cross-linked aromatic copolyesters is their ability to undergo further processing in the solid state through interchain transesterification reactions.