Enthalpies of solution of hybrid perovskites CH3NH3PbX3 (X = Cl, Br, I) in DMSO were measured using solution calorimetry. Standard enthalpies and Gibbs free energies of formation of CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites from halides as well as from elements at 298 K were calculated on the basis of experimental data obtained and compared with the data available in literature. Excellent agreement was obtained between the standard Gibbs free energy of decomposition of CH3NH3PbX3 into solid PbX2, gaseous HX and methylamine calculated on the basis of our data and that evaluated on the basis of vapor pressure measurement results reported by other authors. Entropy contribution was shown to play a major role in the stability of hybrid organic-inorganic perovskites with respect to their decomposition on constituent halides. (C) 2017 Elsevier Ltd.