Interleukin –13 is a recently characterized cytokine which is though to play a role in allergic asthma .The study includes sixty asthmatic children thirty patients suffering from acute exacerbation of their asthma while the other thirty patients are in between the attacks. Their ages ranged from 5-18 years of age. Twenty healthy age and sex matched children were included in the study as controls.Patients and controls were subjected to full history taking, complete clinical examination, complete blood picture, total serum IgE level and chest X ray. IL-13 in serum was measured in all studied children (patients and controls) by using an enzyme- linked immunosorbent assay (ELISA) technique.Statistical analysis of results showed a highly significant difference in the serum level of IL-13 between patients and controls.Serum IL-13 levels are also found to correlate positively to the severity of asthma attack. Thus, IL-13 production is upregulated in bronchial asthma . Moreover, IL-13 may reflect the severity of airway inflammation.IL-13 represents an important mechanism by which inflammatory events in the airway microenvironment can be regulated and represents a potential target for novel anti-inflammatory therapies in allergic asthma. IL-13 may become a key therapeutic target in the future treatment of allergic diseases.