Isothermal vapor-liquid equilibrium data for the binary system hydrogen sulfide + carbonyl sulfide were measured in the temperature range from 232 to 293 K using the static synthetic technique. From the isothermal P - x data, the azeotropic conditions were derived. The critical line of this system was visually detected in a flow apparatus. Interaction parameters for this binary system were fitted simultaneously to all the experimental VLE and critical data for the Predictive Soave-Redlich-Kwong group contribution equation of state.