The equilibrium fractionation factors for the partitioning of deuterium between pure water and water vapor at several temperatures (19¿--27¿C) and between aqueous salt solutions and water vapor as a function of salt concentration at 20¿C are reported. The fractionation factors for the salt solutions show a linear variation with salt concentration and depend on the nature of both the cations and the anions in solution. One molal solutions of the salts show the following differences (in parts per thousand) from the pure water factors: NaCl, -2.3; KCl, -2.5; CaCl2 -4.9; MgCl2, -9.2; AlCl3, -17.2; NaBr, -3.3; NaI, -4.6; Na2CO3, -5.2; Na2SO4, +0.7; K2SO4, +0.7; and seawater (0.31 m), -1.6. Geochemical applications of the results are discussed.