To examine the role of the vagal pathway on the cardiopulmonary functions in NO2‐exposed rats, phenyl diguanide, which stimulates type J receptors in the lungs, was injected to control and exposed rats at a constant dose. Based on a statistical test, a decrease in the heart rate (HR) after the injection was observed in the groups exposed to 20 ppm NO2for 1.5 h and 3 h, and 10 ppm for 24 h. On the other hand, an increase in respiratory rate (RR) was observed in the groups exposed to 10 ppm for 3 h and 4 ppm for 1 wk. No change in HR and RR was found in the group exposed to 0.4 ppm for 4 wk. These results suggest that the augmentation of the reflex cardiopulmonary responses due to stimulation to the type J receptors was produced by exposures with a higher concentration of NO2