To evaluate the relationship between inflammatory markers and asthma severity in children, the amount of interleukin(IL)-8 and granulocyte-macrophage-colony-stimulating-factor (GM-CSF) released by peripheral-blood-mononuclear-cells (PBMC), exhaled nitric oxide (FENO)levels, p65 NF-B subunit and phosphorylated IB (p-IB) expression by PBMC were assessed in 6 controls, 12 steroid naives intermittent and 17 moderate asthmatic children. To investigate their predictive value, biomarker levels were correlated with the number of exacerbations during a 18 months follow-up period. We found that GM-CSF release was higher in moderate and intermittent asthmatics than in controls, whereas IL-8 release was higher in moderate than in intermittent asthmatics and controls. FENO levels were similar among study groups. In moderate asthmatics, IL-8, GM-CSF and FENO significantly correlated with the exacerbation numbers. Moreover, p65 and p-IB levels were greater in moderate than in intermittent asthmatics and controls. According to GM-CSF, IL-8 and FENO levels, two distinct subgroups of moderate asthmatics (low- and high-producers) were identified. High producers experienced more exacerbations than low producers. This study shows ongoing inflammation associated with biological and clinical heterogeneity in moderate asthmatics in spite of regular treatment, and proposes that large prospective studies confirm the importance of biomarkers to assess inflammation and asthma control in asthmatic children.