 Asthma is a chronic inflammatory lung disease characterized by airway hyper-responsiveness and reversible airway obstruction. Over the last decade, the prevalence of asthma is on the rise and it disproportionately affects more women than men. As much as 40 of women with asthma are known to have worsening of asthma symptoms and lung function prior to menstruation. This syndrome is being increasingly recognized as premenstrual asthma PMA. The pathologic differences in female asthmatics with and without this syndrome are not known. The evidence regarding the role of sex hormones has been contradicting. We propose an observational cohort study to examine the changes in airway inflammation in women with asthma in relation to their menstrual cycle and their association with sex hormone levels. In addition we will include women on oral contraceptives to determine their effect on airway inflammation and asthma symptoms. 