To measure the evaporation rate of solids in vacuum, the evaporating substance was condensed on a water-cooled lead plate. The plate with the condensate was removed, irradiated by neutrons, and etched in a mixture of nitric and hydrofluoric acids, and the radioactive isotopes in the solution were identified.The possibilities of the method are illustrated by the measurement of the molybdenum metal and zirconium carbide evaporation rates. The amount of molybdenum (99Mo) was determined by directγ-spectrometry of the solution. In the case of zirconium, radiochemical isolation of95Zr from the mixture of antimony, zinc, tantalum, and hafnium present in the solution in amounts commensurable with that of zirconium was suggested.The vaporization experiment was carried out in a vacuum ~10−5to 10−6Torr. The measured values of the molybdenum and zirconium carbide evaporation rates in the temperature range ~1900 to 2400°C are given.