PESTAB. The amount of information on feline toxicology is sparse. Much has been concluded from a few clinical cases, from experimental work, and by extrapolating information from other species. Cats are said to be quite sensitive to benzyl benzoate, a miticide, and should not be subjected to it. Rotenone, derived form the derris plant and used as an insecticide, is considered relatively nontoxic, will occasionally cause nausea and vomiting in cats, and produces liver damage in cats ingesting it from their fur. Chlorinated hydrocarbons known to be toxic to cats are DDT, TDE, methoxychlor, lindane, chlordane, toxaphane, dieldrin, aldrin, and endrin. The cat is poisoned by walking or lying on contaminated surfaces or by topically applied pesticides in which the toxin is ingested with subsequent grooming. They can also be absorbed through the skin and ingested in poisoned insects. The oral minimum lethal dose for DDT is about 250 mg/lb. For endrin the oral lethal dose is 3 to 6 mg/kg; aldrin, 15 mg/kg; dieldrin, 500 mg/kg. For cutaneously applied endrin it is 150 mg/kg; aldrin, 75 mg/kg; dieldrin, 750 mg/kg. These compounds act on the central nervous system and chronically cause both hepatic and renal degeneration. They are stored in fat, excreted in milk, cross the placenta and remain for long periods as residues in soil. Members of the organophosphate group include ronnel, Co-ral, malathion, parathion, dichlorvos, tetraethyl pyrophosphate, dioxathion, trichlorfon, ruelene, dicapton, diazinon, and fenthion. This group produces its effect by completely inhibiting acetylcholinesterase, thus allowing acetylcholine to exist in excess. The carbamates used in insecticides for plants and animals are relatively nontoxic. Arsenic poisoning may arise from its use in ant poisons, herbicides, snail bait, and insecticides. The use of strychnine may also result in poisoning, when used as a pesticide or in malicious poisonings. Metaldehyde, used in snail bait, has not been reported as poisonous to the cat. However, the cat is quite susceptible to the rodenticides sodium fluoracetate and fluoracetamide which are colorless, odorless, and tasteless. ANTU (alpha naphthyl thiourea) is an odorless, bitter-tasting, bluish-gray powder used as a rodenticide which has an LD50 for the cat of 75 to 100 mg/kg. Thallium has poisoned cats either by direct ingestion or by ingesting poisoned rodents. Warfarin, pindone, and diphacinone, are all anticoagulants, which inhibit prothrombin synthesis by interfering with the action of vitamin K. Zinc phosphide, a commonly used rodenticide, produces anorexia, colic, lethargy, coma, and asphyxiation. Alpha chloralose, used both as a rodenticide and an anesthetic agent in rodents, acts both by depressing and stimulating the central nervous system. The cat has been used to study methylmercury toxicity as this species manifests similar clinical and pathological features to those of man. The cat would appear to be a useful sentry to potential dangers to man from environmental mercury.