Density and ultrasound measurements of propranolol hydrochloride in aqueous solutions were carried out as functions of the drug molality, in the presence of different concentrations of added electrolyte (0.00, 0.01, 0.03, and 0.05) mol kg(-1) NaCl and at the temperatures (288.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K. The critical micelle concentrations were determined using the Phillips definition. To calculate changes in the thermodynamics properties of micellization, the mass action model was applied.