A process for controlling hydrogen sulfide emissions and corrosivity in geothermal systems has been evaluated on a small laboratory pilot plant scale and shown to be technically feasible. The hydrogen sulfide was oxidized by oxygen injected directly into a 11.4-liter-(3-gallon)-per-minute flowing stream of simulated geothermal brine. The oxidation of the sulfide was complete at oxygen:sulfide mole ratios of 1.25:1 to 1.5:1, depending on temperature and total dissolved solids in the brine. The reaction products were free sulfur, sulfite and sulfate. The ratio of these was dependent upon the oxygen:sulfide mole ratios; but, generally, more than 80% of the sulfide was converted to sulfate, approximately 10% to free sulfur and less than 10% to sulfite