Abstract: A hydrogen generator for hydrolyzing hydrides substantially at stoichiometry to provide hydrogen on demand to a fuel cell is disclosed. The generator comprises a sealable, pressurizable, thermally insulated vessel into which a hydride in granular form is loaded. Water, most of which may be a byproduct from the fuel cell, is controllably introduced into the vessel for reaction with the hydride to generate hydrogen. The rate of introduction of the water is determined by the demand for hydrogen at the fuel cell. Heat transfer apparatus is disposed about the vessel to control the temperature of the reaction. A stirring mechanism is disposed in the vessel to prevent clumping of the hydride, to distribute the water to unreacted hydride, and to disperse the heat of the reaction throughout the hydride mass and thence to the heat transfer apparatus. An outlet from the vessel is provided for transfer of the generated hydrogen to the fuel cell.