The effects of hydrogen peroxide on citrinin and ochratoxin A toxicity were examined using HeLa cells. The citrinin was completely detoxified by prior incubation with 0.05% hydrogen peroxide for 30 min at room temperature, and the toxic compound(s) that resulted from heating citrinin at 100 degrees C were also detoxified upon reheating it with hydrogen peroxide. On the other hand, ochratoxin A was not detoxified by hydrogen peroxide at room temperature, but its toxicity was reduced by heating ochratoxin A with hydrogen peroxide under alkaline conditions.