Heat capacities of the spin crossover complex [Fe(2-pic)(3)]Cl . MeOH (2-pic: 2-picolylamine or 2-aminomethylpyridine) were measured with an adiabatic calorimeter between 12 and 355 K. A broad heat capacity peak, starting from similar to 80 K, culminating at similar to 150 K, and terminating at similar to 250 K, was observed. The temperature range of the heat capacity anomaly corresponds to that where the: low-spin and high-spin states coexist in the Fe-57 Mossbauer spectra. The enthalpy and entropy changes arising from the heat capacity anomaly were 8.88kJ mol(-1) and 59.5 J K-1 mol(-l), respectively. The entropy gain was much larger than the contribution expected from the change in the spin-manifold R In 5;(13.4 J K-1 mol(-l)) where R is the gas constant. The-remaining entropy gain is attributed to the contribution from the change in the internal vibrations. On the basis of the domain model, the number of molecules per domain was found to be very close to unity, implying a very weak cooperativity in the spin crossover occurring in the solid state of this complex.