Levels of pro-allergic cytokine IL-4 are increased in asthmatic airways, contributing to allergic inflammation. The purpose of this study was to define the effect of treatment with triamcinolon, montelukast, and formoterol on serum level of IL-4 and IgE, clinical parameters (symptom score, FEV1) and bronchial hyperreactivity (BHR) in children with moderate asthma. It was 8 week, placebo-controlled and randomized, double blind trial of 99 children with moderate atopic asthma allergic to dust mite. Patients were randomly allocated to receive 400 mg triamcinolon (n = 20), 5 or 10 mg (according to age) montelukast (n = 18), 24 mg formoterol (n = 19), or placebo (n = 42). 80 children completed the study. After treatment with triamcinolon, montelukast, and formoterol the level of IL-4 in blood serum in all study groups significantly decreased, and all clinical parameters improved; treatment with triamcinolon, formoterol, and montelukast had no effect on IgE level in serum. Mean IL-4 levels in serum before and after treatment with triamcinolon were 0.129 pg/ml with 95% Cl, 0.1-0.145 pg/ml and 0.086 pg/ml with 95% Cl, 0.023-0.109 pg/ml respectively (p = 0.02); with montelukast were 0.123 pg/ml with 95% Cl, 0.57-0.82 pg/ml and 0.102 pg/ml with 95% Cl, 0.62-0.82 pg/ml respectively (p < 0.001); with formoterol were 0.128 pg/ml with 95% Cl, 0.108-0.164 pg/ml and 0.113 pg/ml with 95% Cl, 0.096-0.146 pg/ml respectively (p = 0.002). No correlations have been found between changes in serum IL-4 and any other clinical parameters after treatment. This study demonstrates that one of the possible ways by which triamcinolon, montelukast, and formoterol contribute to inhibition of allergic inflammation is by decreasing IL-4 levels.