Liver concentration of the reduced form of glutathione is increased by chronic lead nitrate administration. Hepatic glutathione content is lowered by acute aflatoxin B1 intoxication while in lead-pretreated rats this decrement is not evident. The administration of lead nitrate which increases liver glutathione also decreases acute aflatoxin B1 toxicity. This provides additional evidence that, in the liver, glutathione concentration plays a role in controlling acute aflatoxin B1 toxicity.