The formation of ZnMoO4 and ZnjMojO? were studied using x-ray diffraction analysis, IR, DTA- TG, electrical conductivity, elemental analysis and surface acidity measurements. The concentration of acidic sites on the surface of MoOj-ZnO system was studied and the results illustrated a maxima at ZnO - MoOj (20-80%) at a calcination temperature of 600°C. The stability of the ZnMoO4 and Zn^MojO^ phases were studied at 600 and 750°C. The ZhjMojO.) phase is stable at lower temperature and disappears at temperatures above - 700°C