Rhinitis is common in asthmatic schoolchildren who are allergic to animal dander and constantly and indirectly exposed to these allergens in their everyday environment. As a patho-physiological linkage between nasal and bronchial inflammation has been proposed to exist, the primary objective of this study was to determine whether nasal administration of mometasone furoate (MSNF) can reduce bronchial inflammation, as reflected in the level of exhaled nitric oxide (FENO) in asthmatic schoolchildren with dander allergy and mild-to-moderate rhinitis. Forty such children were assigned randomly to be treated for 4 wk with MSNF or placebo, employing a double-blind procedure. FENO was the primary end-point measured and secondary end-points were nasal levels of NO, the concentration of eosinophilic cationic protein (ECP) in nasal lavage, the relative numbers of eosinophils in blood, forced expiratory volume in 1 s (FEV1), peak expiratory flow (PEF) and scoring of symptoms. There was no significant difference in the FENO values of the treated and control groups at any time-point, whereas the nasal level of ECP was lower in the treated group compared with placebo (p = 0.05) on both days 7 and 28, and compared with baseline for the treated group (p = 0.06 on day 7, p = 0.02 on day 28). Furthermore, the mean blood eosinophil count decreased in the treated group, which also demonstrated lower scores for nasal symptoms compared with placebo, but neither of these differences were statistically significant. FEV1, PEF and nasal levels of NO remained unchanged in both groups. Four weeks of nasal treatment with MSNF had no effect on bronchial inflammation, as reflected by exhaled NO, whereas signs of nasal and systemic eosinophil activation were reduced. Thus, nasal administration of a steroid as a strategy to reduce asthmatic inflammation remains questionable in mild-to-moderately severe cases of perennial rhinitis and asthma.