C/W2B5 composites were fabricated from an in situ reaction between B4C, WC and carbon black powders by hot pressing. High flexural strengths of 852.8 and 786.2 MPa, high fracture toughness of 8.04 and 8.89 MPa m(1/2), high hardness of 11.83 and 12.25 GPa, and rather low electrical resistivity of 0.61 and 0.6 mu Omega m were obtained for C-70W(2)B(5) material hot pressed at 1900 and 2000 degrees C, respectively. The mechanical properties and electrical conductivity decreased with reducing W2B5 content. It seems that this extremely high flexural strength and hardness are ascribed to the high relative density and formation of network of W2B5 grains, and high fracture toughness are attributed to the crack deflection resulting from the bridging and pullout of plate-like W2B5 grains and the weak interface between W2B5 and carbon, and the residual stress. The high fraction of W2B5 and higher degree of graphitization contribute to the excellent electrical conductivity. (c) 2005 Elsevier B.V. All rights reserved.