The solubilities of behenic acid in supercritical CO, with and without ethanol cosolvent were determined at 308.15 K and 318.15 K in the pressure range from 8.0 to 16.0 MPa, and the concentration of cosolvent ranged from 0 to 6.5 mol%. The corresponding density of the fluid phase was also determined. The effects of the cosolvent concentration, fluid density, pressure, and temperature on the solubility are discussed. The solubility increases with ethanol concentration, pressure, and the apparent density d(1) (moles of CO2 per liter of the fluid) of CO2 at higher ethanol concentrations.