Rationale: Mannitol challenge tests are used to identify individuals of bronchial asthma. Exhaled nitric oxide (FENO) and sputum eosinophils are also used as noninvasive diagnostic tools for bronchial asthma. Therefore, we purposed to identify those diagnostic findings in patients with clinical diagnosis of bronchial asthma. Methods: Total 463 subjects who were suspected as having bronchial asthma were enrolled and their clinical data was analyzed. Skin prick test with common inhalant allergens was done to identify atopic status. Serum total IgE levels were measured by immunoCAP system. They were performed mannitol challenge test (Aridol?, Pharmaxis). Their induced sputa were analyzed for differential count. FENO was measured by NIOX MINO (Aerocrine AB, Sweden) at that time. Results: Mean age of the subjects was 45.60±14.39 years and 44.5% (206 subjects) were male. Atopy prevalence was 49.8%, and mean total IgE level was 195.91±323.78 IU/L. Ninety four subjects (21.2%) have positive responses in mannitol challenge tests. One hundred forty six (31.5%) out of all subjects had clinical diagnosis of bronchial asthma. Among them, mean FENO level was 47.28±37.67 and sputum eosinophils were 4.68±13.52. The levels of airway hyperresponsiveness were significantly correlated with FENO and sputum eosinophils (P＜0.001 for FENO, P=0.001 for sputum eosinophils). Conclusion: Theses findings suggest that FENO and sputum eosinophils may have a complementary role in diagnosis of bronchial asthma to mannitol challenge test.