The fracture toughness and hardness of Ce-Y-TZP ceramics with various compositions are studied by using Vickers indentation. It is found that crack mode of Ce-Y-TZP belongs to Palmqvist crack under loads less than or equal to490N. The hardness is enhanced with increasing mol% YO1.5, while this trend is depressed with the increase of CeO2 content. Samples with compositions located in the vicinity of t --> m boundary tend to possess higher toughness. The closer the compositions near t-phase boundary of t-m, the higher the fracture toughness of Ce-Y-TZPs due to the increase of transformability or operation of relevant toughening mechanisms. A(s) temperature and tetragonality of t-phase are regarded as the ease of degree in the t --> m transformation, and the relation between A(s) temperature and tetragonality with K-1c value are further explored. (C) 2002 Elsevier Science B.V. All rights reserved.