Asthma is the most common allergic disease giving rise to the morbidity or school absence in children and has an increasing incidence worldwide. montelukast is a well known leukotriene receptor antagonist used to treat children with asthma. Several cytokines in addition to IgE are known to affect the course of the disease and response to treatment in this regard. This is a double blind prospective interventional cohort study done in Kerbala Pediatric Teaching Hospital during January, 2011 through February, 2013. One hundred sixty doctor-diagnosed asthmatic children and 30 healthy control were recruited in this study. Of them selected 60 participated in the placebo-controlled cohort study (according to past drug history) and 100 participated in the gene-environment interaction study. The current study aims, in part, to test the effect of cytokine profile and serum IgE level (measured by ELISA) on asthma development and their influence on 1-month course of montelukast.