Problems of the safe and long-term operation of live steam and hot reheat conduits of 800-MW power-generating units are discussed. The condition of the metal of steam conduits of 800-MW units is analyzed using the data of nondestructive testing, studies of the properties of cutout specimens, and computations of the remaining life after various operating periods. It is shown that long-term service of metal in steam conduits, which have been produced by different methods from large-diameter pipes of steel 15Kh1M1F, at domestic and foreign plants softens the metal considerably. In some cases, impermissible defects in the form of cracks and other damage accelerate the failure. Computations made with allowance for the actual condition of the structure and properties of pipes show that the service life of live steam conduits from standard 465 × 75 mm pipes and hot reheat conduits from 920 × 32 mm pipes fabricated from steel 15Kh1M1F should be limited to 150.0 and 130.0 thousand hours, respectively, at design steam parameters.