The effect of temperature on the reaction of gamma-Al2O3-modified Al powders with distilled water was investigated. It was found that by increasing the temperature up to 40 degrees C, the hydrogen generation speed can be enhanced one to two orders of magnitude relative to that at room temperature (18 degrees C). X-ray analyses and transmission electron microscopy observations revealed that the reaction by-product at 40 degrees C is bayerite (Al(OH)(3)), which is chemically neutral. The present results imply that slightly increasing the temperature is an effective way to get the target hydrogen generation speed.