The object of the invention is to provide a stampable sheet of reinforced thermoplastic material, the sheet being composed of a plurality of layers of polyester material and a plurality of layers of reinforcing material integrally formed together, the central layer or layers of polyester material being of more slowly crystallizing material than the outer layers. The polyester layers are all substantially amorphous and are made of polyester polymers selected from poly(ethylene terephthalate), selected copolymers of poly(ethylene terephthalate), poly(1,4-cyclohexylenedimethylene terephthalate), selected copolymers of poly(1,4-cyclohexylenedimethylene terephthalate), blends of poly(ethylene terephthalate) and any of the aforementioned selected copolymers, and blends of poly(1,4-cyclohexylenedimethylene terephthalate) and any of the aforementioned selected copolymers, The central polyester layer or layers are polyester polymers selected from the aforementioned selected copolymers and blends.Another object of the invention is to provide a stamped sheet from the stampable sheet of reinforced thermoplastic material, the stamped sheet having a heat deflection temperature under 264 psi. load greater than T.sub.m -50.degree. C.