In the present investigation, the ZrB2 powder is produced by SHS of mixture containing H3BO3, ZrO2 and Mg. The thermal analysis and XRD study reveal the reaction mechanism of ZrB2 formation by SHS process. Synthesis of H3BO3-Mg System results in formation Of Mg-3(BO3)(2) and MgB4 phases, whereas ZrO2 is partially reduced to ZrO3 and Zr during synthesis of ZrO2-Mg system. The reaction between elemental Zr and MgB4 results in ZrB2 formation. The particle size of ZrB2 is found to decrease with the addition of SHS diluent. (c) 2007 Elsevier Ltd. All rights reserved.