al/sub 2/o/sub 3/-15 vol. percent zro/sub 2/ bar shaped composite specimens were fabricated by pressing three layers. the two outer layers consisted of al/sub 2/o/sub 3/ and unstabilized zro/sub 2/ (primarily in the monoclinic polymorph), and the inner layer consisted of al/sub 2/o/sub 3/ and partially stabilized zirconia in the tetragonal polymorph. the transformation of zro/sub 2/ from tetragonal to monoclinic, upon cooling from sintering temperature, led to the establishment of residual compressive stresses in the outer layers. flexural tests at room temperature showed that residual stresses contributed to strength increasing from 450 to 825 mpa. the existence of these stresses was verified by measuring apparent fracture toughness, as well as using strain gages. strength and toughness data were obtained at 500, 750. and 1000 degrees c. x-ray diffraction was used to explain the elevated temperature data by monitoring the monoclinic to tetragonal transformation upon heating to 1000 degrees c