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In situ synthesis of bulk Al(3)BC(3) was achieved via a reactive hot-pressing method using Al, B(4)C, and graphite powders at 1800 degrees C for 2 h. The reaction path for synthesizing Al(3)BC(3) was investigated. It was found that Al(3)BC(3) formed via the reaction of C, B(4)C, and Al(4)C(3) above 1180 degrees C. Dense Al(3)BC(3) was prepared with a little B(4)C and graphite remained. Microstructure observations revealed the plate-like morphology of Al(3)BC(3) grains. Moreover, the mechanical properties of Al(3)BC(3) were characterized (Vickers hardness of 11.1 GPa, bending strength of 185 MPa, fracture toughness of 2.3 MPa.m(1/2), and Young's modulus of 163 GPa). Young's modulus decreased slowly with increasing temperature, and at 1600 degrees C remained 79% of that at ambient temperature. These results show that Al(3)BC(3) is a promising lightweight high temperature structural material.