Superoxide disproportionation may partially account for the noteworthy radioprotectant activity of bis(3,5-diisopropylsalicylato)copper(II) [CuII(3,5-dips)2]. Groups of mice treated with CuII(3,5-dips)2 3 or 24 h before exposure to a lethal dose of gamma-radiation had survival rates of 33% and 58%, respectively. These results suggest that copper complexes might be developed for protection of normal tissues in association with cancer radiotherapy and protection against occupational exposures to hazardous radiation.