The progress made on process engineering and bench-scale investigations of the General Atomic Company sulfur-iodine thermochemical water-splitting cycle is presented. A second generation process engineering flowsheet is under development. The results of this new flowsheeting effort not only represent a reiteration in the process engineering, but they also reflect the progress made in the laboratory; at the time of writing, approximately 60% of the flowsheet is complete. It is expected that the thermal efficiency of the process will be 45% higher. In 1977, bench-scale investigations of the sulfur-iodine cycle have been initiated with the objective of verifying the practical chemical feasibility of the cycle. One of three subunits, which performs the main solution reaction, has been built and is undergoing startup. The other subunits are planned to be ready for testing by 1979, and operation of the integrated unit is expected late in 1979.