Obstructive sleep apnea (OSA) leads to increased cardiovascular morbidity and mortality, which have been attributed to intermittent hypoxia (IH). The effects of IH on lung structure and function are unknown. We used a mouse model of chronic IH, which mimics the O2 profile in patients with OSA. We exposed adult C57BL/6J mice to 3 months of IH with an FIO2 nadir of 5%, 60 times/hr during the 12hr light phase. Control mice were exposed to room air.