The purpose of this study is to investigate the biological H-2 and CH4 potential based on the nature of organic waste materials in a two-stage thermophilic fermentation process. Three varieties of actual waste specifically potato, kitchen garbage and bean curd manufacturing waste (okara) were selected. The production rates for H-2 and CH4 were as follows: potato, 2.1 and 1.2 l/l/d; garbage, 1.7 and 1.5 l/l/d; okara, 0.4 and 1.4 l/l/d in the continuous processes. The H-2 and CH4 yields were 20-85 ml H-2/g VSadded and 329-364 ml CH4/g VSadded, respectively. The H-2 yield increased and the CH4 yield decreased in the order of potato, kitchen garbage and okara. The H-2 yield was shown to be not only dependent on the proportion of carbohydrate but also on the hydrolysis pH of the organic waste, which was influenced by the nature of the organic waste materials. Higher yields of H-2 or CH4 were obtained when the hydrolysis pH of the organic waste was close to the optimum pH range of H-2-producing bacteria or methanogenic archaea in the two-stage fermentation processes. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.