The tensile, creep and stress-rupture databases for alloy 800H (UNS N08810) were assembled and analyzed with the intent of extending the allowable stresses in ASME Section III, Subsection NH for service to 500,000 h at 1400°F (760°C) and below and recommending new allowable stresses for limited service times to temperatures as high as 1650°F (900°C). Values for SY1 and SU were produced for the temperature range of 800 to 1650°F (425 to 900°C). These include a revision of existing values to 1500°F (800°C). Values for Sm were produced for the same temperature range. Values for the minimum stress-to-rupture, Sr, were produced for the temperature range of 800 to 1650°F (425 to 900°C), including a revision of existing values to 1400°F (750°C).