In a recently performed case-control study, characteristics of the airway microbiota in suboptimally controlled adult asthmatics were compared with those of healthy, nonasthmatic adult subjects. Bacterial burden was significantly greater in asthmatic subjects. Further, increased airway microbiota variability and diversity were correlated with increased bronchial hyper-responsiveness. Although several limitations are present, this study provides an intriguing initial insight into the possible relationship between the airway microbiota and asthma pathogenesis.