Inhaled corticosteroids (ICS) control airway inflammation in mild to moderate asthma by reducing inflammatory gene expression. However, incomplete understanding of the molecular mechanisms underpinning corticosteroid action hinders development of improved therapies for more severe disease. Microarray analysis was performed on RNA from biopsies taken from healthy individuals after receiving single dose of ICS to characterize corticosteroid-induced modulation of gene expression in the human airways. Healthy male, non-smoker, non-allergic volunteers (age 18-50 years) with normal lung function were recruited into a prospective, double-blind, placebo-controlled, randomized, two-period crossover study involving an initial screening visit, followed by two intervention visits. Participants were screened at visit 1 for fulfilment of the study eligibility criteria. At visit 2, volunteers were randomized to receive inhaled budesonide (1600 µg) or placebo, both via Turbuhaler. Two to three weeks later, at visit 3, participants received either budesonide or placebo, as appropriate to complete both study arms. Six hours after placebo or a budesonide inhalation, bronchial biopsies were obtained via bronchoscopy.