Publisher Summary The presence of oxygen in the environment presents both advantages and threat to all forms of life. The use of oxygen as a final electron acceptor provides more energy than that afforded by anaerobic fermentation. Oxygen is also useful in many biosynthetic reactions. Superoxide radicals are normal and common by-products of aerobic existence. Superoxide dismutases are indispensable for protection against the toxicity of superoxide radicals. The evolution of three types of SODs to accomplish the same reaction in different organisms attests to their vital role in aerobic survival. Moreover, recent developments in the regulation of MnSODs, and the success in cloning FeSOD and MnSOD genes of E. coli, and the isolation of regulatory mutants can certainly open new research avenues to better understand the regulation of these enzymes. Finally, the knowledge gained from E. coli will make it possible to explore the regulation of SODs in other organisms. We look forward to active and exciting developments in SOD research.