and !man Harfoush Pediatric and Clinical pathology Departments, Benha Faculty of Medicine, Zagazig University ABSTRACT Background: T- helper cells can differentiate into at least two subtypes secreting distinct profiles of cytokines, Thy and Th2, regulating immunoproteclion and different immunopathologies. Interleukin-4 (IL-4) is both the product and the inducer of The cells. This study was done to clarify the role of this immunoregulatory cytokine (IL-4) in pathogenesis of bronchial asthma. Method; This is a cross-sectional study on 35 asthmatic children as well as sex and age matched 20 normal children as controls. Interleukin-4 (IL-4) was estimated in sera of asthmatic children (during attacks and after remissions as well as controls, as a product of T-cell activation. Results: There was a significant difference between serum levels of 1L-4 pg/ml during attacks of asthma and after remissions, they were (30.16+22.79 pg/ml) and (16.24+13.78 pg/ml) respectively; (p=0.03). Also, there was no significant correlation between serum level of IL-4 pg/ml and absolute cosinophilic count cell/m1 and serum level of IgE 11../ml during attack where (r=0.078), (r=0.006) respectively. A positive correlation was recorded between serum (IL-4 pg/ml) and age of children (r=0.43) during attacks. Conclusion: T-Cell activation is associated with high levels of serum interleukin-4 during attacks of bronchial asthma, the arrangement for treatment of activity of bronchial asthma by anticytokines must be put into consideration in future in our country