The nuclear energy driven thermochemical cycle is one of the potential water-splitting processes for producing hydrogen, presumed to be the transportation fuel of the future. A life cycle assessment (LCA) of one such system, which utilizes nuclear energy to drive the ISPRA Mark 9 thermochemical cycle, is presented in this paper. The results of the LCA are presented in terms of the emissions of greenhouse gases (CO2-equivalent) and acid gases (SO2-equivalent). The contributions of the thermochernical plant to the emissions were determined through the estimation of material and energy requirements for chemical inventory, raw materials consumption and plant fabrication/installation. The greenhouse gas emissions from the system are 2515 g CO2-equivalent kg(-1) H-2 produced and acid gas emissions 11.252 g SO2-equivalent kg(-1) H-2 produced. A comparison of this hydrogen production route with other routes, including steam reforming of methane and high-temperature electrolysis, is also presented in the paper. (c) 2006 Society of Chemical Industry