Acute inhalation toxicity was evaluated in groups of 10 Sprague-Dawley rats (5 male and 5 female) exposed to parachlorobenzotrifluoride at nominal concentrations of 6.03, 20.8, 28.4, 39.1, or 66.7 mg/l for 4 hours. Mortality was observed in 4 animals in the 28.4 mg/l dose group, in 6 animals in the 39.1 mg/l dose group, and in 8 animals in the 66.7 mg/l dose group. The LC50 value was determined to be 33.0 mg/l (95% confidence limits of 22.2 to 49.2 mg/l) for a 4 hour exposure period. Clinical observations during exposure included: redness around eyes; muscle spasms; labored breathing; reduction in activity or prostration; excessive salivation and lacrimation; mucoid nasal discharge; and partially closed eyes. Clinical observations made in the 14 day post exposure period included: red and mucoid nasal discharge; soft stool; labored breathing; excessive lacrimation; hypersensitivity to sound; increased activity; dry rales; yellow staining of the ano-genital region; aggressive behavior; poor condition; uncoordinated movement; limb ataxia; partially closed eyes; alopecia; hair loss; rapid breathing; red penis discharge; and chromodacryorrhea. Observations on gross necropsy of decedents and animals surviving to the end of the 14 day observation period included: lung discoloration; enlarged lungs; dark red foci in lungs; liver discoloration (in animals dying spontaneously); gas filled stomach and intestines; and kidney discoloration.