Interleukin-5 (IL-5) is thought to play a pivotal role in the pathogenesis of asthma. The aim of this study was to determine the level of serum IL-5 during exacerbation and remission of asthma and to asses IL-5 role as a marker for therapeutic response in partly controlled atopic asthmatic children in relation to a control group of healthy children. Pulmonary functions, eosinophils in peripheral blood and IgE & IL-5 concentration in serum were measured in 20 normal control subjects and in 40 allergic asthmatic children with partly controlled asthma before and after treatment. Results: After 2 months of treatment, with ICS and montelukast, significant decreased levels of IgE, IL-5 and peripheral blood eosinophils. Conclusion: Both ICS and LTA have similar effects on the improvement of all parameters