The vapour pressure of uranium was determined between 1720 and 2340°K: –log Pu(atm)=(26,210 ± 270)/T–(5.920 ± 0.135). The heat of sublimation calculated therefrom is ΔH°s, 0 (U)= 129.0 ± 2.0 kcal/g atom. This result is in agreement with independent measurements of the vapour pressure of uranium as well as with the values derived from thermochemical cycles based on the dissociation energies of the monoxide and dioxide of uranium and on the vaporization of the monocarbide, the dicarbide and the monosulphide of uranium.