There is a very high prevalence of OSA in obese individuals and a high prevalence of obesity in patients with OSA. The pathophysiology of OSA is intimately linked to obesity. Anatomic and functional considerations of the pharyngeal airway, the CNS, central obesity, and leptin likely interact in the development of OSA in obese individuals. OSA may itself predispose individuals to worsening obesity because of sleep deprivation, daytime somnolence, and disrupted metabolism. The diagnosis of OSA requires the clinician's awareness of its potential to cause a spectrum of acute and chronic neurocognitive, psychiatric, and nonspecific symptoms in patients who may be unaware that their sleep is disturbed. Symptoms and examination findings help predict which obese individuals have OSA, and polysomnography is the gold standard by which to make the diagnosis and assess the effects of treatment. Numerous disease states are associated with both OSA and obesity, and it is becoming clear that the relationships are mediated by complex interrelated mechanisms. Common diseases and disease mechanisms in OSA and obesity suggest that conditions related to obesity may be better managed if patients, particularly those who are morbidly obese, are evaluated and treated for previously undiagnosed OSA. OSA is cured in only specific cases with craniofacial or upper airway surgery, and the general application of UVP is not efficacious. OSA also can be cured with sufficient lifestyle-mediated or surgical weight loss; however, in the absence of long-term weight maintenance, OSA returns with weight gain. Although not curative, nasal CPAP is the initial treatment of choice for most patients because of its noninvasive approach and technical efficacy. It is limited, however, by patient acceptance and long-term compliance. Advances in mask comfort and use of humidified air should increase its acceptance. Future management strategies include newer generations of positive airway devices that automatically titrate pressures (which are not yet recommended by expert organizations) and multidisciplinary approaches to managing the care of patients with OSA.