Glutaric anhydride (GA), an industrial chemical, was found of moderate acute peroral lethal toxicity with LD50 values (95% confidence limits) in the rat of 1.41 (0.80-2.49) g/kg (males) and 0.54 (0.36-0.79) g/kg (females), with death being due in part to gastrointestinal irritancy. Dilution with water given by gavage after peroral dosing had no effect on lethal toxicity. Acute percutaneous LD50 values (rabbit) by 24-h occlusion were 6.25 (5.34-7.33) g/kg in males and 5.66 (3.21-9.95) g/kg in females; local skin effects included erythema, edema, necrosis and ulceration. A 6-h exposure to a statically generated saturated vapor atmosphere (rat) produced no signs of toxicity or irritancy. A 4-h, but not 1-h or 3-min occluded contact with 0.5 g of moistened GA (rabbit) produced erythema, edema and necrosis. Contamination of the eye (rabbit) with 10 mg GA produced conjunctivitis (hyperemia, chemosis and discharge) which persisted 7 to 14 d, mild iritis of 2 to 14 d duration, and mild to severe corneal injury which healed within 14 d. A maximization study in guinea pigs by the method of Magnusson and Kligman showed no potential for skin sensitization with GA. The major acute hazards of GA were by swallowing, eye contact and sustained skin contact.