BACKGROUND AND OBJECTIVE:: METHODS:: RESULTS:: A total of 50 asthmatic adults and 54 controls were enrolled (mean age 43.8 years). The sensitivity and specificity of mannitol challenge (defined by a PD15 of <635 mg) were 48.0% and 92.6%, respectively, whereas those of methacholine (defined by a PC20 of <16 mg/mL) were 42.0% and 98.1%, respectively. Twenty asthmatic participants (24%) showed positive response to a single agonist only. In the receiver operating curve analyses using response–dose ratio values, area under the curve was 0.77 (95% confidence interval (CI): 0.68–0.86) for mannitol, and 0.89 (95% CI: 0.83–0.95) for methacholine. The correlations between log- transformed mannitol and methacholine response–dose ratios were significant but moderate (r = 0.683, P < 0.001). CONCLUSIONS:: SUMMARY AT A GLANCE: Methacholine and mannitol bronchial challenge are two representative tests for asthma. However, their difference has not been directly evaluated among Korean adults. We compared the diagnostic properties of these two tests. Two diagnostic tests showed similar diagnostic properties, but also suggested their intercomplementary roles for asthma.