ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 and boron added alloys have been prepared and dispersion of polyaniline (PANI) has been performed on ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 + 1 wt% B by ballmilling. Structural and micro-structural characterizations of these materials have been carried out by XRD and SEM, respectively. Hydrogen absorption pressure-composition (P-C) isotherms have been obtained for ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5, ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 + 1 wt% B and ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 + 1 wt% B + 25wt% PANI in the temperature and pressure ranges 30-100 degrees C and 0.1-30bar, respectively using a hi.-h-pressure Seiverts' apparatus. The effect of particle size on the hydrogen absorption kinetics of ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 and ZrMn0.85Cr0.1 V0.05Fe0.5Ni0.5 + 1 wt% B alloys have been studied. From the hydrogen absorption kinetics, the activation energy of dissolved hydrogen in ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 - H, (ZrMn0.85Cr0.1 V0.05Fe0.5Ni0.5 + 1 wt% B) - H and (ZrMn0.85Cr0.1V0.05Fe0.5Ni0.5 + 1 wt% B + 25 wt% PANI) - H has been calculated and the results have been discussed. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.