The heat treatment of stearic acid shows a zero-order process which is in accord with an evaporation process. In this study, the melting points of three samples of stearic acid (A, B, and C) from the rising temperature experiments at the heating rate (beta) of 2-12 degrees C min(-1) are found to be in the range of 57.4-73.5 degrees C and that of stearic acid B in N-2 flow rate ranging from 50 to 1000 ml min(-1) is 69.0-70.0 degrees C. From the DTA signals, the beta of 6-8 degrees C min(-1) and an N-2 how rate of 100 ml min(-1) were found to be the optimum conditions for the evaporation process of these materials. The enthalpy of vaporization (Delta H-vap) of stearic acid is calculated by the use of the Antoine [1] and Clausius-Clapeyron equations [2]. These Delta H-vap values are equal to 115.7 and 81.6 kJ mol(-1) for the temperature ranges of 349-415 and 457-649 K, respectively. These values can be compared to the activation energy (E-act) which is in the range of 87.0 to 101.1 kJ mol(-1) determined from the rising temperature experiments of three types of stearic acid subjected to various experimental conditions. Generally, E(act)greater than or equal to Delta H-vap. It is predicted, and verified experimentally, that the equilibrium vapor pressure and the coefficient of vaporization have a logarithmic relationship.