The influence of an animal's copper (Cu) and manganese (Mn) status on its response to ozone was investigated in weanling mice. Control, Cu-deficient and Mn-deficient mice were exposed continuously to 1.2 ppm O3 or filtered air for 7 days. In control mice, ozone exposure resulted in higher lung activities of CuZnSOD, MnSOD and GPx. In contrast, Mn-deficient mice did not display increases in lung MnSOD, CuZnSOD or GPx activities following ozone exposure. Similarly, ozone-induced increases in lung CuZn-SOD and MnSOD activities were not observed in Cu-deficient mice, although lung GPx activity was increased in these mice relative to their air-breathing controls. These results show that an animal's Cu and Mn status can influence its response to ozone, and the data suggest that Cu- and Mn-deprived animals may be more susceptible to long-term or repetitive ozone exposure.