Serum eosinophilic cationic protein (ECP) and soluble low affinity receptor for IgE (Fc epsilon RII/sCD23) concentrations were measured in relation to symptom-medication scores, pulmonary function, and total IgE levels in 27 chronic allergic asthmatic children (17 boys, 10 girls), mean age 10.8 years, before and at the end of a three month inhaled corticosteroid (budesonide) treatment period, Serum ECP and sCD23 concentrations were also measured in age matched non-asthmatic controls with allergic rhinitis. All asthma patients had significantly higher serum ECP and sCD23 than the controls, whereas the mean serum IgE was not different. No correlation between total IgE concentrations and serum sCD23 could be detected in either group; At the end of the treatment period, symptom-medication scores and pulmonary function improved. Serum ECP and sCD23 concentrations were reduced; however, total IgE values did not change significantly. A significant relation was found between the improvement of symptom-medication scores and fall in both sCD23 and ECP concentrations. Although there was a significant correlation of pulmonary function values with serum ECP, no such relation was observed for sCD23. It appears that serum sCD23 and ECP concentrations could be good disease markers, particularly in asthma. Monitoring of serum inflammation markers, especially ECP, may be useful in the follow up of asthmatic children on anti-inflammatory treatment.