The sulfasalazine melting temperature and, molar enthalpy have been determined by the DSC method. The shake flask method has been used to measure the drug solubility in buffer solutions (pH 2.0 and 7.4), hexane, and octanol and to determine the distribution coefficients in the octanol/buffer systems in the temperature range of 293.15-313.15 K. The calculated thermodynamic functions were then used to study the influence of the solvent type and sulfasalazine protolytic properties on the drug dissolution and distribution.