Modulation of human lung airway physiology by commensal microbiota has become one of the key mechanisms involved in the pathogenesis of adult asthma. Recent evidence suggests that the composition of respiratory microbiota plays a significant role in the manifestation of adult asthma; however, scientific evidence about the relationship between airway microbial diversity and phenotypes of adult asthma is limited. Further research is needed to understand the interactions between the airway microbiota and host immune response to develop microbiota-based strategies in management of adult asthma. This study reviews the advances in culture-independent methods for detection of airway microbiome, the current data about airway microbiota in healthy individuals and in adult patients with asthma with a focus on bacterial communities, and the future research directions in airway microbiome.