The occurrence of residues of chlorinated hydrocarbon insecticides in animal tissue has been well established in the literature. Thomas et al (I); Fahey and Brindley, (2); Entomology Research Division (3) are three authors who reported the contamination of beef tissues resulting from the feeding of treated forage or permitting livestock to forage on pesticide treated crops. Davich et al (4), reported the occurrence of insecticide residues in swine tissues taken from animals permitted to feed on clover pasture treated with insecticides. Street (5), reported the reduction of dieldrin storage in tissue of rats treated with DDT. Cook and Wilson (6), Wilson and Cook (7), and Cook (8), have shown that dieldrin is constantly being recycled from the blood of cattle to the gastro-intestina l tract, that phenobarbital increases levels of many liver microsoma! detoxifying enzymes, and that charcoal can be utilized as an antidote for dieldrin poisoning in ruminants. Since swine are monogastric animals rather than ruminants and under farm conditions are under a fat accumulation regime rather than a maintenance or loss diet as are milking cattle, doubts arose as to the possibility of utilizing this technique in eliminating dieldrin residues in swine. Preliminary experiments showed that feeder pigs permitted to forage in stover grown on aldrin or heptachlor treated soil may accumulate up to 0.I ppm of dieldrin or heptachlor epoxide. The purpose of this study was to determine whether phenobarbital and charcoal would reduce the storage of dieldrin in the fatty tissue of swine.