The tensile and stress-rupture properties of a Nextel 610 reinforced alumina-yttria material are examined at temperatures up to 1093°C (2000°F). Microscopy on virgin and tested specimens indicate that initial matrix damage in the form of matrix microcracks exists in as-received materials and does not increase during testing. Pushout testing indicates no significant change in interface frictional stress during testing. Therefore, the mechanical damage driving stress-rupture is deduced to be concentrated in the fibers. A model has been developed which relates the composite stress-rupture lifetime to single fiber rupture data and which includes the effect of pre-existing matrix cracking. This model contains no adjustable parameters. While the creep deformation and trends in lifetime are accurately captured by this technique, the composite lifetimes predicted using single fiber rupture data are smaller than observed.