A method of accurately manipulating the pressure of helium gas in the rangeP=10−1to 10−20Torr,T<5 K is presented. The method requires only a very modest apparatus and makes use of thermodynamic measurements on the4He–Grafoil system. A calibration curve and a pressure scale for the manometer are developed which will allow convenient application in other laboratories. An experiment which utilizes the technique is briefly disscussed.