Thermoplastic compositions comprising, in intimate admixture, polyethylene terephthalate, a rubber-free copolymer of or a rubber-modified graft copolymer of a vinyl aromatic compound and an .alpha.,.beta.-unsaturated cyclic anhydride, a fibrous modifier, and a nucleating agent are disclosed. These compositions display desirable properties, particularly elevated heat deflection temperatures and good surface appearance.Also disclosed is a process for producing articles by injection molding the compositions at a hold pressure of about 5,000 to about 10,000 psi.