The melting point of stoichiometric uranium monophosphide (UP) was found to be 2610 ± 20°C. The pellet was sealed in a tungsten crucible and gamma radiography was used to determine when the sample had filled the lower crucible cavity. The UP was stoichiometric before and after melting and was presumed to be in equilibrium with its vapor at elevated temperatures. Composition of the melted material and the reaction between UP and tungsten were examined using x-ray diffraction, metallographic and chemical analysis.