Flowsheet modeling of the molten cadmium-cadmium oxide thermochemical cycle indicates that hydrogen may be produced at efficiencies approaching 58% (LHV) based on high temperature solar energy delivered to the process. Experiment studies and fluid dynamic/chemical kinetic modeling are being used to verify the flowsheet assumptions and design an "on sun" demonstration of the cycle. Key steps under investigation are the generation of hydrogen from steam and molten cadmium and the recovery of the high temperature solar products without excessive recombination. Laboratory work in progress includes: (1) hydrolysis of molten cadmium, and (2) measurements of the decomposition of cadmium oxide and recombination of cadmium with oxygen in a modified thermo-gravimetric/mass spectrometric apparatus. Rapid hydrogen generation from molten cadmium has been demonstrated. The decomposition/recombination experiments indicate that the decomposition temperature may be reduced to 1300°C in the presence of inert gas. Results of the laboratory studies are coupled with fluid dynamic/chemical kinetic modeling to design the solar cavity/decomposition reactor and evaluate alternate means of quenching the decomposition products. These results feed back into an updated flowsheet and the design of the "on sun" demonstration.