Background: Obesity and asthma remain two of the fastest growing and mostpervasive public health problems in developing countries. Obesity has been shown toincrease the risk of asthma and wheezing. Both disorders may share common geneticand environmental causes. There are mechanical, developmental, hormonal andimmunological reasons for their effects. Given the parallel increases in obesity andasthma, it is not surprising that the prevalence and incidence of asthma and its relatedsymptoms and phenotypes have been increasingly associated with body mass indexand obesity. The cross sectional diagnosis of asthma has been associated with obesityin both children and adults.Aim of work: The aim of our study is to assess the relation between differentgrades of body mass index, serum leptin & pulmonary functions (lung volumes &spirometry) in patients with bronchial asthma.Subjects and methods: Our study included 2 groups, 52 asthmatic patientswith different grades of body mass index and 10 controls with different grades ofbody mass index. They were subjected to full history taking, clinical examination,chest x-ray, demographic data acquisition; age, sex, BMI and waist to hip ratiocalculation, pulmonary function test (spirometry & lung volumes), serum leptinmeasurement by ELISA.Results: there was a statistically significant difference in BMI among thedifferent body built subgroups and this was due to significant change in the weightamong the different body built subgroups. As regards statistical comparison ofspirometric data of the large airways in different body built subgroups there wasstatistically significant difference in the mean value of FEV1 post-bronchodilator.While the spirometric data of the small airways and lung volumes subdivisions werefound to be statistically insignificant in different body built subgroups. The presentstudy found statistically significant difference of the mean value of serum Leptin indifferent body built subgroups. It was much higher in the obese subgroup than othersubgroups.Conclusion: We can conclude that increased body weight was associated withincreased incidence of asthma whether this was due to changes in airway diameter oralternative mechanisms concerning increased work of breathing due to decreasedchest wall compliance or other mechanical factors. Also the association betweenasthma and serum leptin is strong and definite because Serum leptin was alwaysfound to be elevated in our asthmatic cases regardless their body weight and thehighest levels were found naturally in the obese subgroup.