The use of a high pressure gas to aid in devolatilization is attractive to many industries. A new experiment has been designed which can test the influence of gases at elevated pressure on the mass transport and thermodynamics of polymer-solvent systems. It is an extension of the inverse gas chromatography (IGC) technique. The new technique, termed high pressure IGC, has been verified with several solvents on a poly (vinyl) acetate capillary column. A description of the apparatus and preliminary results are presented in this chapter.