Small amounts of hydrogen in hydrogen storage alloys, such as Mg2Ni, were detected using neutron radiography (NRG). Hydrogen concentrations in a hydrogenated solid solution were determined by this technique. Furthermore, we were able to obtain NRG images for an initial stage of hydrogen absorption in the hydrogen storage alloys. NRG would be a new method of measurement to clarify the behavior of hydrogen in hydrogen storage alloys. (C) 2000 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.