An automatically operated carbon dioxide reduction system was developed, fabricated and tested. The system was designed to reduce the carbon dioxide equivalent to that produced by one man, and to produce carbon and oxygen. A system such as this is required for providing respiratory support for man on extended space missions. The program was conducted in three phases: (1) development of system components, (2) experimental determination of system design parameters, and (3) fabrication and testing of an engineering model. Successful operation of the engineering model demonstrated the feasibility and ease of operation of the system. Recommendations are made for improving the system and for future work. (Author).