Effect of N,N-diethyldithiocarbamate (DDC), an inhibitor for cytosolic superoxide dismutase, on an ionomycin-induced increase in oxidative metabolism was examined in cerebellar neurons dissociated from the rats, using a flow cytometer and 2',7'-dichlorofluorescin diacetate and fluo-3-AM, fluorescent dyes for intracellular hydrogen peroxide and Ca2+, respectively. DDC reduced the ionomycin-induced augmentation of 2',7'-dichlorofluorescin fluorescence in a dose-dependent manner. DDC did not affect cellular content of 2',7'-dichlorofluorescin and ionomycin-induced increase in intracellular Ca2+ concentration. Results indicate that ionomycin increases the formation of superoxide anion in brain neuron.