The heat capacities of tetrakis(methylthio)methane C(SCH3)(4) were determined at the temperatures T = (13 to 360) K by using an adiabatic calorimeter. Three first-order phase transitions were observed, whose temperatures and enthalpy and entropy gains were determined as follows: transition from phase III to II, T-trs = 296.23 K, Delta(trs)H(m) = 7.09 kJ.mol(-1), Delta(trs)S(m) = 23.935 K-1.mol(-1) transition from phase II to I, T-trs = 318.76 K, Delta(trs)H(m) = 7.29 kJ.mol(-1), Delta(trs)S(m) = 22.87 J.K-1.mol(-1); transition from phase I to liquid, T-fus = 338.89 K, Delta(fus)H(m) = 3.31 kJ.mol(-1), Delta(fus)S(m) = 9.77 J.K-1.mol(-1). The highest temperature crystalline phase I can be assigned as an orientationally disordered state, which is established by two-step phase transitions. The entropy gains at the phase transitions occurring in the solid state are well accounted for in terms of thermal excitation of the reorientational molecular motions in the crystal lattice. Based on the transition entropies, the present study clearly predicts that the most reasonable space group of phase II is not I4/mmm(D-4h(17)) reported so far by X-ray diffraction, but I (4) over bar(S-4(2)). This conclusion supports the assignment previously derived from Raman Spectroscopy.