The solubility of ketoprofen in acetone + water as a function of temperature has been determined at the round temperature values 10-49 degrees C. The solubility diagram exhibits five regions : one homogeneous zone, three two-phase zones (two liquid-solid equilibria and one liquid-liquid equilibrium), and one three-phase zone. The density and viscosity as a function of concentration in the binary mixture ketsprofen + acetone are also reported. Some equations are proposed to correlate the experimental results.