A detailed analysis of the oxidation of zinc sulfide particles was conducted in a thermobalance between 548 and 630 degrees C with different oxygen concentrations. It was found that, in the presence of external mass-transfer effects, an oxysulfate intermediate was formed. However, when the flow rate was chosen such that this effect was eliminated, no sulfates were formed. Analysis of the controlling regimes indicated that even the use of small particles (<200 mesh) did not eliminate internal diffusional resistance. Thus, using only the initial rate data, the surface reaction model (-r=kK(A)[O-2]/1 + K-A[O-2]) with no dissociation of oxygen was found to depict the data very well up to 609 degrees C. Simple power law models were found to be wholly inadequate to represent the data.