The Nuclear Hydrogen Initiative (NHI) of the U.S. Department of Energy's Office of Nuclear Energy Science and Technology is supporting an effort to reevaluate thermochemical cycles reported in the literature as having both promising efficiencies and proof-of-concept results. Nine cycles were identified. A group of universities was tasked with the evaluation of these cycles using the NHI consistent methodology for calculating efficiency and for recommending and conducting critical research needed to help in the down-selection process. Argonne National Laboratory coordinated these activities. This paper provides an overview of the program and summarizes the results of the down-selection process. Individual papers that contain the details of the research are provided by the universities. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.