BACKGROUND: Bronchial asthma is one of the most common illnesses in children. Factors influencing development of asthma have not been studied in rural population. MATERIALS AND METHODS: Two thousand school-going children from three schools of Sonapur VDC, Sunsari in the surrounding of industries were screened for the presence of symptoms of asthma using a questionnaire suggested by International Study of Asthma and Allergy in Children (ISSAC). RESULTS: One hundred twenty children were identified with symptoms of bronchial asthma. For each child with asthma two age and sex matched non-asthmatic control were selected from the study population. History, clinical examination and in-depth interview were carried out for all cases and controls. Factors associated with presence of symptoms of asthma on multivariate analysis were: passive smoking (OR 3.33, 95% CI 1.85-7.65), pets at home (OR 5.5, 95% CI 1.04-29.15), and absence of windows in living rooms (OR 4.03, 95% CI 1.17-13.79). Factors such as family history of asthma, history of worm infestation, fuel used for cooking, location of kitchen and food allergy were not significant in statistical analysis. CONCLUSION: Thus, passive smoking, inadequate ventilation and domestic animals and pets (dogs and cats) at home are significant risk factors associated with presence of symptoms of asthma in these children.