Toxicological evaluation was made on the effects of two peripheral sensory irritants (tear gases): 1-chloroacetophenone (CN) and dibenz[b,f]-1,4-oxazepine (CR). Animals had a 15-min daily inhalation exposure to average vapour concentrations of 87.6 mg CN m-3 or 1008 mg CR m-3 (both equal to 0.05 LC50) for 5 or 10 days and were sacrificed 24 h after the last exposure, when biochemical and histopathological observations were made. Both chemicals caused a significant decrease in body weight gain. Histological changes in lung, liver and kidneys were more severe after 10 than after 5 days of exposure and were more severe in CN-exposed than in CR-exposed mice. Organ weight to body weight ratios remained normal except for the spleen to body weight ratio, which decreased in CN-exposed mice after both 5 and 10 days of exposure. Biochemical indicators showed a toxic response only in CN-exposed mice, but the only consistent change was an increase in blood glucose. Hepatic alkaline phosphatase was not influenced, malondialdehyde concentration and acid phosphatase activity were increased only after 5 days of exposure and liver GSH concentration decreased after 10 days of exposure. Results indicate that CN is not only more toxic than CR in absolute terms but is also more toxic at the 5% level of their LC50.