Obstructive Sleep Apnea (OSA) and type 2 diabetes mellitus are two prevalent medical conditions with significant associated cardiovascular and cerebrovascular morbidity and mortality. Research indicates that the prevalence of OSA is increased in diabetic patients when compared with normoglycemic patients and that OSA is independently associated with type 2 diabetes. Further research suggests that effective treatment of the OSA with continuous positive airway pressure (CPAP) improves insulin responsiveness in both non-diabetic OSA patients and diabetic-OSA patients. We are proposing a clinical trial to evaluate the impact of 6 months of CPAP therapy on glycemic control in type 2 diabetic patients with OSA.