A rotating-bomb combustion calorimeter specifically designed for the study of sulfur-containing compounds has been assembled and calibrated. Thianthrene has been used as a secondary standard in order to verify the chemistry of the combustion process and the accuracy of the energy corrections involved in the analysis of the results. With this calorimeter, the energy of combustion of 1,3-dithiane has been determined. The vapour pressure of 1,3-dithiane has been measured over a temperature range of about 15 K by the Knudsen effusion technique. From the experimental results, the following quantities for 1,3-dithiane atT = 298.15 K have been derived: ΔfHmo(cr) = −(65.6 ± 2.2) kJ·mol−1, ΔsubHmo = (62.9 ± 0.7) kJ· mol−1, and ΔfHmo(g) = − (2.7 ± 2.3) kJ· mol−1. A comparison of these results with data for 1,3-dioxane and other reference molecules was carried out. The support of the Spanish DGICYT under Project PB96-0927-CO2-01 is gratefully acknowledged. H. F. would like to acknowledge the Fellowship grant from the CONACYT (M´exico).