The cytotoxic effects of oxygen radicals have been studied in enriched population of mature bovine oligodendrocytes in culture. Oxygen radicals were generated enzymatically by glucose and glucose oxidase, and hypoxanthine and xanthine oxidase combinations. Cytotoxicity was assessed by trypan blue exclusion and percentage lactate dehydrogenase release into the culture media. Incubation of bovine oligodendrocytes with these oxygen radical‐generating systems for 4 hr resulted in significant cell death, especially in the glucose oxidase system. The oligodendrocytes were completely protected by catalase from the cytotoxic effects of both oxygen radical generating systems. However, superoxide dismutase, dimethylsulfoxide and antioxidants such as vitamin E and glutathione did not protect oligodendrocytes from the oxidant‐mediated cytotoxicity. It appears that hydrogen peroxide produced in these oxygen radical‐generating systems gives rise to toxic radicals that induce the cell death of bovine oligodendrocytes in culture.