Thermochemical water-splitting cycle is a promising process to produce hydrogen using solar or nuclear energy. R&D on hydrogen production through iodine sulfur (IS) thermochemical cycle was initiated in 2005 at INET. Fundamental studies on the three reactions of IS cycle, i.e., Bunsen reaction, HI decomposition reaction, sulfuric acid decomposition reaction, and related techniques, such as separation, concentration and purification, were carried through. In Bunsen section, the reaction kinetics and separation characteristics of H(2)SO(4) and HIx phases were studied. In HI section, Pt catalysts were loaded on different supporters by various methods and used for HI decomposition; and electro-electro-dialysis(EED) was developed for concentration of HI acid. In sulfuric acid section, non-Pt catalysts were developed for SO(3) decomposition. Based on fundamental researches, a closed-loop test apparatus of 10 NL/h H(2) was designed and established. The current status of IS process research is summarized in this paper. In addition, R&D plan of IS process at INET is presented. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.