Transient nuclear heating experiments have been carried out on gas-bonded, refractory-metal-clad uranium monosulfide specimens in the Transient Reactor Test Facility. The range of temperatures attained extended to the fuel melting point of 2462° C., Although some fuel slumping was observed, the specimens did not suffer the mechanical damage and fragmentation found for uranium dioxide samples tested earlier. In this respect, the uranium monosulfide behavior is considered to be more satisfactory from the standpoint of safety. The general behavior of the uranium monosulfide samples was consistent with its material properties.