There is a critical need to develop animal models that can characterize the potential of respiratory allergy. Dust-mite allergens are one of the major etiological agents in the induction of allergy and asthma in humans. In this study, the effects of intratracheal injection with dust-mite allergen were investigated by analyzing the in vivo proliferative response of lung-draining hilar lymph nodes and histopathological changes in the lung parenchyma. Balb/c mice were inoculated intratracheally with dust-mite allergens, a mixture of Dermatophagoides farinae and D. pteronyssinus dissolved in phosphate-buffered saline, or with an equal volume of saline alone. After 1 week, all the mice were injected intravenously with radioactive (3)H-thymidine and sacrificed 5 h later so as to assess the radioactivity incorporated into the hilar lymph nodes. The results indicated a marked increase in the proliferative response in the hilar lymph nodes of the animals treated with the dust-mite allergen as compared to the response of the control group. Treatment with dust-mite allergen also caused perivascular and interstitial eosinophilic inflammation of the lungs, hyperplasia of bronchus-associated lymphoid tissue, and an increase in the eosinophil peroxidase activity in the lungs. These results indicate that intratracheal injection with dust-mite allergen can trigger a number of changes consistent with respiratory allergy, including an increased proliferation in the draining lymph nodes.