The pressure-volume-temperature (PVT) data for polymer/gas solutions is an important fundamental property of which accurate measurement has not been reported until recently. The diffusivity, solubility and Surface tension are critical physical properties of polymer/gas systems for understanding and controlling polymer processing such as foaming, blending, extraction reaction and so on. However, the determination of these properties relies on accurate PVT data as a prerequisite. in this study, we have developed a new methodology for measuring the PVT properties of polymer melts Saturated with high-pressure gas at elevated temperatures. This paper presents a description of the methodology, including the experimental apparatus design and data analysis. A case Study on neat polypropylene (PP) density measurement and determination of PP/CO2 Solution Volume swelling was presented to elucidate and verify the methodology at high-pressure and high-temperature conditions. (C) 2008 Elsevier B.V. All rights reserved.