Dense sintered composites of ZrO 2 (2 mol% Y 2 O 3 ) and WSi 2 have been fabricated by hot isostatic pressing for 2 h at 1500°C under 196 MPa. They contain a small amount of W 5 Si 3 ; during sintering, WSi 2 decomposes into W 5 Si 3 and amorphous Si. The ZrO 2 particles in the composites consist of only t-ZrO 2 . Microstructures and mechanical properties are examined, in connection with ZrO 2 content. The fracture toughness and bending strength of the composite with 40 mol% ZrO 2 addition are 7.1 MPa m 1 / 2 and 1011 MPa, respectively.