Authors have proposed a new hydrogen production system that simultaneously produces hydrogen and hydrogen peroxide by water electrolysis. Experimental apparatus of the system is composed of a hydrogen electrode with platinum meshes, a hydrogen peroxide electrode with carbon material and an electrolyte with Nafion(R). In this paper, the superiority of the system is outlined, and the experimental results of the electrolytic synthesis of hydrogen and hydrogen peroxide from water are reported. Hydrogen peroxide is synthesized at the high efficiency when some kinds of carbon material are used as the hydrogen peroxide electrode. Furthermore, the possibility of applying the solar energy to this system is also discussed. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.