Adsorption of H, on multiwalled carbon nanotubes was measured at 77 K by a volumetric method. Adsorption and desorption isotherms are largely reversible. The adsorption capacity increased remarkably after receiving heat treatment at 400 degreesC and being pressed into pellets. The isotherms show typical feature of supercritical adsorption and were satisfactorily modeled by the model that applied for usual supercritical adsorption. The maximal adsorption capacity of hydrogen under the condition tested is less than 0.5 wt%. (C) 2003 Elsevier B.V. All rights reserved.