Dense sintered composites of ZrO2 (2 mol% Y2O3) and WSi2 have been fabricated by hot isostatic pressing for 2 h at 1500 degrees C under 196 MPa. They contain a small amount of W5Si3; during sintering, WSi2 decomposes into W5Si3 and amorphous Si. The ZrO2 particles in the composites consist of only t-ZrO2. Microstructures and mechanical properties are examined, in connection with ZrO2 content. The fracture toughness and bending strength of the composite with 40 mol% ZrO2 addition are 7.1 MPa . m(1/2) and 1011 MPa, respectively.