DTA, TGA and X-ray diffraction analysis of a low-quality zinc concentrate from Maidanpek deposit in Yugoslavia have been made. High content of marmatite has been found in it, which results in the formation of ZnFe2O4 when roasted. Behaviour of Yugoslavian concentrate during oxidation is compared to those of Bulgarian, Polish and Canadian concentrates. The results obtained from the thermal treatment of the concentrates and the calculations made, make possible to recommend optimal composition of mixtures for roasting in fluid bed. They are made up of Bulgarian, Polish and Canadian concentrate and Yugoslavian concentrate in them should be up to 8%.