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TiB_2-B_4C ceramic composites containing no additives were hot-pressed from a mixture of TiB_2 and B_4C powders containing 0 up to 100 mol%B_4C (20 mol%). Hot-pressing was conducted at 1950℃ for 3.6 ks under a pressure of 31.2 MPa in an Ar gas atmosphere. The mechanical and electrical properties were examined as a function of compositional change from TiB_2 to B_4C. TiB_2-B_4C composites containing 20-60 mol%B_4C had a relative density of 97.4-98.9%, Vickers hardness of 23.8-27.2 GPa, flexural strength of 589-705 MPa, Young's modulus of 490-568 GPa, fracture toughness (K_<IC>) of 6.46-8.95 MPa・m^<1/2>. The mean surface roughness (R_a) was 25.6-30.5 nm and the electrical conductivity 0.30-3.96 MS・m^<-1>. Thus, these composites possessed a high electrical conductivity and a smooth surface. Their mechanical properties were 1.5 times higher than those of pure TiB_2 or B_4C ceramics, and comparable to those of SiAlON or hot-pressed Si_3N_4 ceramics. The present composites are suitable as ceramic mold materials, machinable by electric discharge, corrosion-resistant electrode components, tool materials and high-temperature structural materials.