The dissociation constant (pK(a)) of (S)-2-hydroxy-4-phenylbutyric acid ((S)-HPBA) was determined at 298.2 K by potentiometric titration. (S)-HPBA exhibits a pK(a) value of 3.81. The solubility of (S)-HPBA in toluene from (288.2 to 343.2) K, in water from (283.2 to 333.2) K, and in ethyl acetate from (278.2 to 313.2) K was measured by the steady-state method. The solubility in all selected solvents increases with the increase of temperature. The solubility of (S)-HPBA in ethyl acetate is much greater than that in water or toluene. Water was found to be a fine alternative to toluene for crystallizing (S)-HPBA and ethyl acetate to be a suitable extraction solvent of (S)-HPBA in the pharmaceutical industry. The experimental solubility data were correlated with the modified Apelblat, Redlich-Kister, Wilson, and universal quasichemical activity coefficient (UNIQUAC) equations, respectively. The Wilson, Redlich-Kister, and modified Apelblat equations show better agreement with the experimental solubility data of (S)-HPBA in toluene, water, and ethyl acetate, respectively. The solubility of (S)-HPBA in aqueous solutions over the pH range from 1.48 to 5.45 at 298.2 K was also determined by the steady-state method, and the corresponding solubility data were separately fitted well with a semi-Henderson-Hasselbalch equation (pH <= 4.0) and a linear equation (pH > 4.0).