Eosinophil-mediated damage to the respiratory epithelium is a major pathogenetic mechanism in asthma. Glucocorticoids have confirmed antiinflammatory properties and effect of formoterol, montelukast and nedocromil on markers of inflammation has been studied. Eosinophil blood counts and eosinophil cation protein (ECP) serum level are often use as markers of clinical monitoring of the disease activity. To evaluate the effect of treatment on allergic inflammation, we measured eosinophil blood counts and ECP serum level, and clinical parameters before and after 4 weeks treatment with triamcinolon, montelukast, nedocromil, formoterol. It was 8 week, placebo-controlled and randomized, double blind trial of 154 children with moderate atopic asthma. Patients were randomly allocated to receive 400 mg triamcinolon (n = 28), 5 or 10 mg (according to age) montelukast (n = 27), 16 mg nedocromil (n = 26), 24 micrograms formoterol (n = 28) or placebo (n = 45). 140 children completed the study. After treatment with triamcinolon and montelukast eosinophil blood counts significantly decreased, after treatment with triamcinolon, montelukast and nedocromil ECP serum level significantly decreased; all clinical parameters improved after treatment with each drug; treatment with triamcinolon had the strongest effect on most parameters (except of FEV1). Mean eosinophil blood counts before and after treatment with triamcinolon were 277.4 and 187.2 cells/mm3 respectively (p < 0.001); with montelukast were 279.6 and 250.7 cells/mm3 respectively (p = 0.002); with nedocromil were 181.7 and 170.1 cells/mm3 respectively (p < 0.183); with formoterol were 276.4 and 264.1 cells/mm3 respectively (p = 0.2). Mean ECP serum levels before and after treatment with triamcinolon were 94.3 and 63.5 micrograms/l respectively (p < 0.001); with montelukast were 85.1 micrograms/l and 71.2 micrograms/l respectively (p < 0.001); with nedocromil were 92.6 and 80.1 micrograms/l respectively (p < 0.001); with formoterol were 95.9 micrograms/l and 87.8 micrograms/l (p = 0.05). We found significant correlation between ECP and hyperresponsiveness after treatment with triamcinolon, montelukast. This study shows that triamcinolon, montelukast contribute to inhibition of allergic inflammation by decreasing eosinophil blood counts and ECP. The serum level of ECP seems to be a good clinical marker of monitoring the disease.