We evaluated the bronchial hyperreactivity (BHR) with a new bronchial challenge test, mannitol dry powder, in a paediatric population with intermittent allergic asthma or allergic rhinitis who did not respond to an exercise challenge test. We selected 50 children, aged 9-16 years, with intermittent allergic bronchial asthma (Group 1) or allergic rhinitis without clinical manifestation of asthma for at least 12 months (Group 2). All patients performed the following tests in three different days (≥ 48 hours apart): Day 1: exhaled nitric oxide (FeNO) determination followed by baseline spirometry and reversibility to inhaled beta2-agonists; Day 2: exercise challenge test followed by FeNO determination; Day 3: mannitol challenge test followed by FeNO determination. Forty children completed the study. Eighteen subjects of Group 1 (90 percent) and 5 subjects of Group 2 (25 percent) resulted positive to the mannitol test. Positive mannitol challenge subjects showed no statistically significant differences compared to negative subjects as regard baseline spirometry, reversibility to salbutamol and response to the exercise challenge test, but they had significantly higher FeNO values. In conclusion, the mannitol challenge test can be a diagnostic tool more useful than the exercise challenge test to identify BHR in a paediatric population with intermittent allergic asthma or allergic rhinitis because it is better reproducible, quick and easy to perform and well tolerated.