The materials used in the construction of the first power gas turbine built by the author’s company are described. These include 19-9 W-Mo for Diesel-engine turbochargers and for the rotating parts of the first 2500-hp 1200 F marine unit. S-590 has been selected for the rotors and blades of the 3000-hp marine units which are being constructed at the present time to operate at 1400 F. Outstanding among the reasons for selection of these alloys is their tendency to good retention of ductility at heat, which should be helpful in minimizing the effect of repetitive thermal stresses which occur upon starting and stopping the turbines, particularly at points of stress concentrations such as blade-root fastenings. Design factors and construction details are discussed from the standpoint of materials for use in machines designed for 100,000-hr life (11½ years). Alloys low in cobalt and columbium are desirable from an economic viewpoint. Processing may be the most important factor in the performance of heat-resisting components. Machined bar stock, forgings, weldments, and castings are felt to be dependable in that order.