Objective This study was carried out to compare chnical efficiency of methylprednisolone (MP) and dexamethasone (Dex) and their effects on Th cytokines in asthmatic children.Methods A total of 39 children with moderate and severe asthma at acute exacerbation were randomly divided into two groups, one (A) with MP 1 -2 mg/kg (n=21) and the other (B) with Dex 0.25 -0.75 mg/kg (n= 18),every 12 -24 h by intravenous drip.Scores of respiratory effort and peak expiratory flow rate prior to and three days after treatment in the asthmatic children aged over five years were evaluated,respectively,as well as the time of wheezing vanishing after treatment.Serum levels of interleukin-2 (IL-2) and IL-4 were determined by radioimmunoassay (RIA) prior to and three days after treatment,respectively.Results There was statistically significant difference in the time of wheezing vanishing between groups A and B (P = 0.042).Three days after treatment,PEER was significantly higher in group A than that in group B (P = 0.025).No statistically significant difference in serum IL-2 and IL-4,as well as ratio of IL-2/IL-4,was found in group B prior to and three days after treatment (P>0.05).Statistically significant difference in serum IL-2 was not observed in group B prior to and three day after treatment (P>0.05),and serum IL-4 decreased significantly (P=0.001) and ratio of serum IL-2/IL-4 (P=0.027) increased significantly three days after treatment than those prior to treatment.No significant correlation between respiratory-effort scores and ratio of serum IL-2/IL-4 prior to treatment was found (P=0.613).Conclusions Up-regulation of IL-2,or inhibition of release of IL-4,probably is not the main anti-inflammatory mechanism of dexamethasone.Methylprednisolone has little effect on serum IL-2,but can effectively reduce serum IL-4, thus increasing the ratio of serum IL-2/IL-4 and counterbalancing function of the Thl/Th2 cells.