In this work, new data are presented for the equilibrium in the system hydrogen sulfide-propane-water-methyldiethanolamine (MDEA). The concentration of the MDEA in the aqueous phase was 3 M. Data for the equilibrium between an aqueous liquid, a non-aqueous liquid and a vapor were obtained for five temperatures between 0° and 100°C and for pressures up to 8.8 MPa.