design criteria and evaluation methods are identified for austenitic alloys that are needed for steam service at 650 sup 0 c and 35 mpa the design criteria are separated into five categories: metallurgical stability; fabrication and joining; mechanical properties; fireside corrosion resistance; and steamside corrosion resistance. in each category alloys that have potential for meeting the design criteria are identified, and methods are outlined for evaluating commercial and developmental alloys against the criteria. alloys falling into the austenite phase field at 650 sup 0 c are potentially the most stable, and the lean stainless steels typified by 17-14 cu/mo stainless steel appear to have adequate strength and fabricability such steels need to be protected from corrosive media by cladding or surface treating. alloys such as 800h have adequate fabricability and steamside corrosion resistance but need improvements in strength and stability. high-chromium steels are best for fireside corrosion resistance but need to be stabilized by large nickel additions research efforts are outlined to improve the corrosion resistance of tubing fabricated from lean stainless steels and to improve the strength of high-chromium alloys. when the evaluation is completed in 1990 a basis will be provided for the selection of the best alloy for subsequent commercialization. 59 refs., 4 figs. (era citation 11: 034283)