NZO/BI mice were given a single gavage of 17.3 µmoles 4-dimethylaminoantipyrine and 58 µmoles sodium nitrite (NaNO2), a dose that produced acute centrilobular necrosis of the liver in 48 hours, due to dimethylnitrosamine formation. The effect of the addition of ascorbic acid in varying concentrations to the gavage mixture was studied. High concentrations of ascorbic acid (2 times the molar concentration of NaNO2) prevented hepatic necrosis. When the concentration of ascorbic acid was reduced to equimolar with NaNO2, the protective effect was incomplete.