GaAs metal-semiconductor field-effect transistors (MESFETs) have been fabricated utilizing thermally stable Pd/Sn and Pd/Sn/Au ohmic contacts fur the first time, MESFETs with Pd/Ge Oohmic contacts are fabricated fur comparison, Thermal stability of the Pd/Sn, Pd/Ge and Pd/Sn/Au ohmic contacts is also presented.