Several kinds of piezoelectric samples were prepared for the experiments on the mechanical strength. By adding an appropriate additives, the bend strength of BaTiO3 ceramics was greatly increased. In the grain oriented (Pb0.8Sr0.2)Bi2Nb2O9 ceramics, a considerable strength anisotropy was found. In a random oriented sample, the thermally diffused impurities injected by vapor phase diffusion of CuO into the grain boundaries increased somewhat the bend strength. The Klc measurement using micro-indentation technique was applied to a hot-pressed pore-free PLZT ceramic sample and the average value was 0.995 MN/m3/2.