Thin Films of LaNi5, intermetallic alloy of thickness 515, 1600, 2155 and 3095 A were prepared by flash evaporation onto the glass substrate at 1.33 x 10(-3) Pa and at room temperature. The in situ variation in resistance due to hydrogen absorption was undertaken and it was found that the Hall effect charge carrier concentration changes sign from -ve to +ve. The content of hydrogen increases with an increase in film thickness. It was suggested that during hydrogen interaction with thin metallic film, hydrogen takes electron from the conduction band of LaNi5, resulting in an increase in the resistance of films. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.