To understand the relative isomeric stabilities of 1,3- and 1,4- diheterocyclohexanes and the ultradiagonal strain energy of thiirane, the enthalpies of formation and sublimation of 1,4-dithiane have been measured. The enthalpy of formation for this compound in the solid state is -69.6 ± 2.3 kJ mol-1, while for the gaseous state, the value is -6.9 ± 2.4 kJ mol. The value for the enthalpy of sublimation is 63.0 ± 0.6 kJ mol-1 Ab initio molecular orbital calculations at the G2(MP2) and at G3 levels were performed, and the calculated enthalpies of formation are compared with the experimental data.