Single subcutaneous injections of rats with methyl methacrylate at a dose of 0.001 cc/g bw caused mild depression, while 0.007 cc/g led to irregular respiration, asphyxia, coma and death. Cats and rabbits subcutaneously injected with doses of 0.0025 cc/g and above showed dose-related depression, irregular respiration, blood in the urine, asphyxia, coma; at doses of 0.0035 and 0.005 cc/g, death ensued. The minimal fatal dose (killing 50 to 90%) for rats administered single doses of methyl methacrylate by gavage was 0.009 to 0.01 cc/g, while 2 doses of 3 cc/g were lethal to cats. Repeated oral doses to rats of 0.005 cc/g every other day for 70 days caused reduced weight gain, blood in the urine, and increased numbers of deaths. Dermal exposure of rats to 1 cc test compound/day for 10 weeks led to edema in all rats, while a repeat exposure on 'hot summer days' caused only temporary local irritation. Single 8-hour inhalation exposure of rats to 30 mg/L of test compound killed approximately 70%, while 11.2 mg/L caused only slight irritation of the upper respiratory tract. Inhalation exposure to 33.5 mg/L led to age-related increased mortality among rats tested at age 12 days (no deaths), 6 weeks (3/5 deaths), or when fully grown (100% mortality). Rats, cats and rabbits exposed to 4.95 mg/L for 18 days, 6 hours/day, by inhalation showed contracted urinary bladders and blood in the urine. Rats and mice exposed via inhalation in constant darkness suffered less mortality than those exposed for 2 to 3 hours of direct sunlight/day. Continuous inhalation exposure of rats (3.5 mg/L for 22 hours), cats and rabbits (15 mg/L for 5 days) was fatal to 1 cat and led to blood in the urine of rats and rabbits, but not the cats. Inhalation (40 mg/L) or subcutaneous injection (2.5 cc/kg bw) caused decreased respiratory rate in both dogs and rabbits without altering blood pressure.