1. It is shown that zirconium boride of the stoichiometric,composition, containing an insignificant amount of impurities, can be produced from commercially-pure starting materials (B4C, ZrO2). 2. A study was made of the influence exerted by the chemical composition and particle size of the starting boron carbide on the chemical and phase compositions of the resultant zirconium boride. As in the case of titanium boride [3], for preparing zirconium boride by the boron carbide method, it is desirable to use a boron carbide with the maximum combined carbon content. 3. It is demonstrated that, during the preparation of zirconium boride by the vacuum-thermal method, the boride becomes thoroughly purified from the contaminants present in the starting materials.