Zirconium carbide-tungsten (ZrC-W) cermets were prepared by a novel in situ reaction sintering process. Compacted stoichiometric zirconium oxide (ZrO2) and tungsten carbide (WC) powders were heated to 2100 degrees C, which produced cermets with 35 vol% ZrC and 65 vol% W consisting of an interpenetrating-type microstructure with a relative density of similar to 95%. The cermets had an elastic modulus of 274 GPa, a fracture toughness of 8.3 MPa.m(1/2), and a flexural strength of 402 MPa. The ZrC content could be increased by adding excess ZrC or ZrO2 and carbon to the precursors, which increased the density to > 98%. The solid-state reaction between WC and ZrO2 and W-ZrC solid solution were also studied thermodynamically and experimentally.