Correlation between the level of reactive oxygen species (ROS) generated by airway inflammatory cells and superoxide dismutase (SOD) activity of pulmonary tissue during an asthma attach was investigated in a guinea pig model of allergic asthma. In addition, the influence of SOD inhibition by diethyldithiocarbamate (DDC, Cu-chelating agent) on the airway was investigated in terms of pulmonary function during an asthma attach. Relative to controls, the capacity of bronchoalveolar lavage fluid (BAL) cells to release ROS was significantly increased in guinea pigs sensitized with ovalbumin (OA) as the antigen, and significantly increased in guinea pigs with an asthma attack provoked by the inhalation of OA. SOD activity was increased significantly in the antigen-sensitized group. The asthma provocation group showed a tendency for increase in total SOD activity, compared with the sensitization group, whose increase was dependent on the increase in copper, zinc-SOD (Cu, Zn-SOD) activity. Pretreatment with DDC increased the severity and duration of the asthma attack. These results were indicated that Cu, Zn-SOD was closely involved in the asthma process, particularly in the scavenging of oxygen radicals secreted from BAL cells.