The problems dealt with in this study concern the oxidation of metal sulfides, in particular attention to the reactions between MSO(4) and MS. The paper contains some experimental results obtained in analyzing the interaction between ZnSO4 and ZnS by means of thermogravimetric analysis, radiomarking using the isotope S-35, X-ray phase analysis and chemical analysis. It was found that irrespective to the molar ratio of ZnSO4 to ZnS, the process has two stages. In the first stage, the following equation may be applied : 11ZnSO(4(alpha)) + ZnS = 4(ZnO.2ZnSO(4)) + 4SO(2) The second stage may be described by the expression 3(ZnO.2ZnSO(4)) + 2ZnS = 11ZnO + 8SO(2) In addition, the effect of the molar ratio of ZnSO4 to ZnS and of the process temperature on the oxidation rate of ZnS mixed with ZnSO4, was determined. The results were compared with those obtained for the oxidation of ZnS in air. The activation energies in both stages of the process were also determined.