The stringent durability requirements approaching 100,000 vehicle miles for automotive substrates and 290,000 vehicle miles for large frontal area diesel substrates for 1994+ model year vehicles call for advanced packaging designs with thick ceramic mats and high mount densities. The latter result in high mounting pressure on the substrate and enhance its mechanical integrity against engine vibrations, road shocks and back pressure forces. A novel measurement technique which applies a uniform biaxial compressive load on the lateral surface of ceramic substrates, thereby simulating canning loads, is described. The biaxial compressive strength data obtained in this manner help determine the maximum mounting pressure and mat density for a durable packaging design. The biaxial compressive strength data for both round and non round substrates with small and large frontal area are presented. This is followed by a comparison of biaxial compressive strength with the triaxial compressive strength and uniaxial compressive strength along the B-axis. It is demonstrated that the B-axis crush strength based on a simple test geometry and efficient test procedure correlates well with the biaxial compressive strength. Improvements in biaxial compressive strength measurement technique are also discussed.