AIM: This study aimed to assess vitamin D status in asthmatic patients and to assess the relationship between vitamin D level and asthma severity. INTRODUCTION: Asthma is heterogeneous disease, usually characterized by variable airflow obstruction and bronchial hyper-responsiveness. The world health organization stated that approximately 300 million people have asthma. Recently the effects of vitamin D appear to have regulatory effect on every part of immune system, vitamin D deficiency being linked to an array of immunologically based disease focusing on asthma. METHOD: The present study included 50 patients diagnosed as bronchial asthma. The asthmatic patient group was divided into group A asthma in between attack and group B exacerbated asthma, that was again divided in subgroup (I), (II), and (III) mild , moderate and severe exacerbated asthma according to symptoms and FEV1. Serum 25 hydroxy vitamin D3 level in all groups was measured by radio immunoassay method and compared between this groups. RESULT : This study shows statistically significant correlation between vitamin D level and severity of asthma. The mean levels of serum 25 hydroxy vitamin D3 in asthmatic patients are: Group A 28.24 ± 1.35 ng/ml, mild persistent: 22.6 ± 11.5 ng/ml, moderate persistent: 18.33 ± 1.31 ng/ml, and severe persistent: 10.45 ± 1.84 ng/ml. P value of <0.01 which is highly significant. CONCLUSION : There was a correlation between asthma severity and vitamin D level. Further studies are needed to determine the role of vitamin D in treatment of bronchial asthma.