Vapor pressures of water over the monohydrate and over the dihydrate of barium chloride were measured from 17 ° C to 72 ° C in a glass apparatus from which air had been evacuated. Equilibrium was approached from higher as well as lower pressures. Vapor pressures for the dihydrate were found to be somewhat lower than previously published values. Vapor pressures for the monohydrate confirm a few published values but are much lower than the values published later in the International Critical Tables. The enthalpies of dehydration of the dihydrate and of the monohydrate were found to be 59 ± 2 kJ-mol(-1) and 56 3 kJ-mol(-1), respectively.