The standard molar energy of combustion of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-thione (thiocamphor), [53402-10-1], has been determined by using a rotary-bomb calorimeter. The vapour pressure of the compound was measured between the interval T = 261.96 K to T = 281.66 K, by the Knudsen-effusion technique. From the experimental results of this work, the standard molar enthalpies of combustion, sublimation and formation in the crystalline and gaseous state at the temperature of T = 298.15 K have been derived for thiocamphor: ΔcHom = -(6736.9 ± 3.3) kJ · mol-1; ΔfHom(cr) = -(86.8 ± 3.5) kJ · mol-1; ΔsubHom = (61.7 ± 0.9) kJ · mol-1; and ΔfHom(g) = -(25.1 ± 3.6) kJ · mol-1. These results have been combined with their gas-phase proton affinities to yield the standard enthalpy of formation of the thiocamphor H+ species. © 1999 Academic Press.