The trichlorobenzenes are a group of three chemical isomers in which three chlorine substituents have been added to a benzene ring. The trichlorobenzenes appear to enter the systemic circulation readily by inhalation, ingestion and dermal absorption; however, data were not available to quantitate the rates of these processes nor of any of the pharmacokinetic processes. The effects in mammals of acute exposure by various routes to trichlorobenzenes include local irritation, convulsions and death. Livers, kidneys, adrenals, mucous membranes and brain ganglion cells appear to be target organs with effects including edema, necrosis, fatty infiltration of livers, increased organ weights, porphyrin induction and microsomal enzyme induction.