Rats were injected with toluene intraperitoneally and the amounts of toluene exhaled were studied. The decrease in toluene in the blood paralleled the decrease in toluene in the exhaled air. The concentration of toluene in the blood attained a maximum after 60 min. and its half life was 180 min. The concentration of toluene in the exhaled air attained a maximum at 90 min, and its half life was 300 min. Twenty-five % of the toluene injected was exhaled and 31% was excreted in the urine. Fifty-six % of the toluene was excreted within 6 hours. The amount excreted in the urine was greater than that exhaled.