Mass spectrometric, torsion effusion, and molecular-beam studies have shown that the vapors in equilibrium with condensed phases of alkali-fluorides, LiF, NaF, KF, and CsF, are usually complex, being mixtures of monomeric, dimeric, and in some cases, trimeric molecules. The total pressures of these mixtures at high temperatures have been measured directly by static method and torsion-effusion method without knowing their vapor compositions. However, for measurements over solid phases where the vapor pressures are lower than 1 × 10 −4 atm, Knudsen-effusion and transpiration methods were employed. The purpose of this paper is to present a method which can be used for the evaluation of the partial pressures of the monomeric and polymeric alkali fluoride species from the total vapor pressure data by use of thermodynamic calculations. The calculations of vapor pressures from experimental observations by use of torsion-effusion, Knudsen-effusion, Langmuir free evaporation, transpiration, molecular-beam velocity-selector, and mass spectroscopic methods are briefly reviewed. The basic thermal data employed for the derivation of thermodynamic properties of crystal and gaseous alkali fluorides are shown. The method of derivation is discussed. Based on the partial pressures and thermodynamic properties of alkali fluorides obtained, the enthalpy changes for the follow reactions: MF(c) = MF(g), MF(c, g) = M +(g) + F −(g), MF(c, g) = M(g) + F(g), M 2F 2(g) = 2MF(g), and Li 3F 3(g) = 3LiF(g), are evaluated, where M = Li, Na, K, and Cs. The vapor compositions of alkali fluorides over the condensed phases in the temperature range 700–2000°K are calculated and plotted.