Hydrogen absorption into Ti electrodes during electrochemical cathodic polarization was monitored using resistometry. Electric resistance of Ti increased with H absorption due to growth of a hydride layer from the surface toward the inside. The growth rate of the hydride layer was estimated from resistance data and was found to depend on the polarization current density, existence of a preformed anodic oxide film, and shape of the specimen. For example, preformation of an anodic oxide film at a potential higher than the breakdown potential, rather, promotes hydrogen penetration. In the case of a thin wire electrode, the hydride layer grew in a nonuniform manner because the volume expansion induced cracking on the surface. Therefore, the average thickness of the hydride layer was estimated from the change in resistance. ©2002 The Electrochemical Society. All rights reserved.