Background: Asthma is a chronic lung disease characterized by wheezy chest, resulting from allergic inflammation and hyperresponsivness of the bronchi to various stimuli. Microbial exposures have been suggested to confer protection from allergic disorders and reduced exposures to gastrointestinal microbes have been proposed as an explanation for the increase in asthma prevalence and severity. Since the general prevalence of Helicobacter pylori has been decreasing, we hypothesized that H.pylori status may be inversely related to the severity of asthma. Aim of Study: This study was coducted to evaluate the relation between Helicobacter pylori infection and bronchial asthma in children. Patients and Methods: The study was carried out on sixty children with asthma who attended to the outpatient clinic of Chest and Allergic Diseases, Pediatric Department, Tanta University Hospital. Also, it included thirty apparently healthy children with matched age and sex who served as a control group. All studied children were subjected to full history taking, complete physical examination, pulmonary function test and detection of H.pylori antigen in stool by ELISA. Data was analyzed by using SPSS. Results: There is significant association between severity of asthma and result of H.pylori so with increase severity of asthma there is decrease in percentage of positive H.pylori results. As regard pulmonary function tests (FEV 1 and PEFR), there was statistically significant difference between positive H.pylori asthmatic and negative H.pylori asthmatic children. There was no statistically significant difference between patient's sex or age and results of H.pylori infection test. Conclusion: There is a significant inverse association between severity of asthma and result of H.pylori infection (by H.pylori Ag in stool). This association is not affected by ages and sex of patients.