This paper deals with enhancement of hydrogen storage capacity for AB(5) type alloy MmNi(4.6)Fe(0.4) from similar to1.5 to similar to2.04 wt%. It has been shown that through suitable processing involving ball milling with specific parameters (200 rpm, 20 min), the alloy particles besides getting fractured to smaller particles also become strained. The maximum strain, increase in lattice constant and unit cell volume are achieved for ball milling parameters of similar to200 rpm and 20 min. It has been suggested that the increase in the unit cell volume results in increase of interstitial hole sizes. This induces higher number of interstitials in unit cell of the material MmNi(4.6)Fe(0.4) to be occupied by hydrogen atoms resulting in increase of hydrogen storage capacity from its value of similar to1.5 wt% obtained in the as-synthesized material to similar to2.04 wt% for ball-milled materials which embody strained particles. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.