OBJECTIVE: Thymic stromal lymphopoietin (TSLP) plays an important role in initiating dendritic cell mediated allergic inflammation. This study was designed to examine the effects of inhaled budesonide on TSLP expression in the lung tissues and on the bronchial-pulmonary pathology in asthmatic rats. METHODS: Thirty-two female Sprague-Dawley rats were sensitized and challenged with inhaled ovabumin (OVA) to induce asthma. The asthmatic rats were randomly divided into 2 groups on the 22nd day of OVA challenge: a budesonide treatment group that received inhaled budesonide at 0.32 mg/kg daily for 7 days and an asthma control group that received inhaled 0.9% normal saline for 7 days. TSLP expression in the lung tissues was measured by Western blot and fluorescent-immunohistochemistry 29 and 36 days after OVA challenge. Bronchial-pulmonary pathological changes were evaluated by hematoxylin & eosin and periodic acid-schiff staining. RESULTS: Budesonide treatment alleviated airway inflammation when compared with the asthma control group 29 days after OVA challenge. However, the airway inflammatory reactions were aggravated in the budesonide treatment group 36 days after OVA challenge (7 days after budesonide discontinuance). TSLP expression in the lung tissues was significantly lower in the budesonide treatment group than that in the asthma control group both 29 and 36 days after OVA challenge (P<0.05). CONCLUSIONS: Inhaled budesonide can inhibit the TSLP expression in the lung tissues and alleviate lung inflammatory reactions in asthmatic rats, but there is end-of-dose failure.［Chin J Contemp Pediatr, 2010, 12 (10):816-819］