The compressibility factor (z) of hydrogen was evaluated from the experimental p-V-T data and calculated from equations of state, such as the SRK equation and BWR equation as well. The effect of z on the adsorbed amount calculated was demonstrated by the adsorption of hydrogen on SA-zeolite. The compressibility factor and the fugacity coefficient of hydrogen were formulated based on the experimental p-V-T data for 60-333 K and up to 25 MPa. (C) 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.