A new procedure for measuring the permeability of a high pressure gas (10.34 MPa) through a polymeric material has been developed. The procedure employs a vacuum system on the low-pressure side of the material. Although it gives a pressure difference of seven orders of magnitude during testing, the real purpose of the vacuum system is to allow the permeability measurements to be made rapidly for a small amount of transported material. The permeability of several commercial polymers to either natural gas or helium has been measured and is reported.