Exhaled nitric oxide (ENO) has been proposed as a marker of airway inflammation in asthma and could be useful to evaluate the response to anti-inflammatory treatment. We investigated the effect of budesonide and nedocromil sodium on ENO levels and lung function in asthmatic children. Twenty stable steroid-naïve asthmatic children were randomized in a single blind, cross-over study to receive inhaled budesonide (group A) or nedocromil sodium (group B) for 6 weeks. ENO was measured with a chemiluminescence analyser at baseline and at the end of each treatment period. Repeated-measures ANOVA was carried out. In asthmatic baseline ENO levels [mean 32.5 ppb, 95% confidence interval (CI) 26.4 to 38.7] were significantly higher compared to reference values (8.7 ppb, 95% CI 8.1 to 9.2, P<0.001). There were no treatment-order effect, no carry-over effect and in both groups the response pattern was the same: budesonide significantly lowered ENO levels from 41.0 ppb to 22.8 ppb in group A (mean, P<0.01) and from 22.6 ppb to 13.0 ppb in group B, (mean, P<0.05), while nedocromil did not reduce ENO values (from 24.4 ppb to 22.6 ppb in group B and from 22.8 ppb to 38.0 ppb in group A, mean, P = NS and P<0.01 respectively). After budesonide treatment ENO values of asthmatics were still significantly higher than in healthy children The baseline values of FEV1 and FEF(25-75) were normal in both groups and no significant changes were observed during the study. In conclusion, our study shows that budesonide, but not nedocromil sodium, significantly reduces ENO levels in stable asthmatic children even in absence of changes in the lung function.