The dimension-stable impregnated polyester tire cord is at least 95% by weight polyethylene terephthalate and has an intrinsic viscosity of 0.70 dl/g to 0.89 dl/g for undrawn cord, a fineness of at least 1100 x 2 dtex, a dimension stability coefficient of at least 30'000 cN.sup.2 /tex.sup.2, a thermal shrinkage of about 0.8 percent measured at a temperature of 160.degree. C. with 0.1 cN/tex pre-stress and a permanent lengthening of less than 1.5 percent at a tire pressure of 2 bar and a temperature of 100.degree. C., so as to reduce shrinkage during vulcanization and in tires heated in operation and so as to provide a quieter running tire. The fatigue resistance of this polyester tire cord suffers a drop in tensile strength of less than 20 percent measured at 10.8 MC with 6 percent strain and 6 percent compression so that tires made from the polyester cord have a greater durability and increased life.