The decomposition and vaporization processes of samarium triiodide were studied. The enthalpy changes associated with the decomposition reaction, SmI3(s) -> SmI2(l) + 1/2I(2)(g), Delta H degrees(298 K) = (117 +/- 10) kJ center dot mol(-1), and the sublimation process, SmI3(s) -> SmI3(g), Delta(sub)H degrees(298 K) = 276 kJ center dot mol(-1), were determined from the temperature dependence of the equilibrium vapor pressures measured extensively in an appropriate temperature interval. The congruent vaporization of samarium diiodide was also studied, and the value for its standard sublimation enthalpy was selected to be Delta subH degrees(298 K) = (292 +/- 5) kJ center dot mol(-1).