Sixty day old male CD rats were exposed by nose only to (14)C-methyl bromide (55 ppm) for three minutes. The data indicated that the liver, lung, and kidney were the major organs of (14)C deposition immediately following exposure. Up to thirty-two hours following exposure, the major routes of excretion were pulmonary (14CO2) and renal with approximately 43% and 21% of the total inhaled radiolabel being eliminated, respectively. In separate experiments, 60 day old CD male rats were exposed by whole body inhalation for 6 hours/day for 1, 5, and 10 days to 30 ppm methyl bromide or control air. Following the 1 day exposure, glutathione (GSH) reductase activity in the liver showed an increase, while GSH S-transferase was significantly increased. Glucose-6-dehydrogenase (G-6-PDH) was increased and nonprotein sulfhydryl content was decreased in the kidney. After 5 days of exposure, GSH transferase activity was significantly increased, while G-6-PDH showed an increase in the lung. GSH reductase activity had decreased in the liver. After 10 days of exposure an increase in G-6-PDH activity was evident in the lung, and a significant decrease in GSH reductase and GSH S-transferase activities were found in the liver.