The stress‐strain curves for 3% cobalt cemented tungsten carbide and sintered diamond compact are determined up to a plastic strain of 8 and 0.2%, respectively, by measuring the permanent deflection at the center of the circular flat face of anvils used in ultrahigh‐pressure experiments. The yield strength based on 0.2% offset for 3% cobalt cemented tungsten carbide is 50±5 kbar, and that for sintered diamond compact ranges from 200 to more than 500 kbar, depending on the sintering quality.