This work presents a pertinent study on the phase behavior of binary systems involving progesterone, in compressed and/or supercritical CO2, propane and n-butane. For the experimental measurements of vapor-liquid (VL) and solid-fluid (SF), phase equilibrium was measured using the synthetic static method with a variable volume cell with a sapphire window for phase transition visualization at temperature ranging from 283 to 368 K and pressure up to 10 MPa. The experimental data obtained were modeled using the Peng-Robinson equation of state (EoS-PR) with the quadratic mixture rule of van der Waals (vdW2). From the data obtained in the present work, it was verified that progesterone presents low solubility in CO2. However, the solubility of this steroid is more pronounced in n-butane and in propane, respectively, when compared with values for CO2. (C) 2008 Elsevier B.V. All rights reserved.