Working materials for making high-purity hydrogen sources suitable for feeding low-temperature fuel cells are analyzed and investigated. Optimal compositions and operational characteristics of hydrogen-accumulating and hydrogen-generating materials are determined. Metal-hydride hydrogen accumulators of repeated action and chemical hydrogen generators of the thermolysis and hydrolysis type are elaborated. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.