Obstructive sleep apnea is an increasingly well-recognized disease characterized by periodic collapse of the upper airway during sleep. This leads to either complete or partial obstruction of the airway, resulting in apneas, hypopneas, or both. This disorder causes daytime somnolence, neurocognitive defects, and depression. It affects almost every system in the body, resulting in an increased incidence of hypertension, cardiovascular disease, stroke, pulmonary hypertension, cardiac arrhythmias, and altered immune function. It also increases the risk of having an accident, presumably as a result of associated somnolence. The gold standard for the diagnosis of sleep apnea is an overnight polysomnogram. Split-night studies are becoming increasingly common and allow for quicker implementation of therapy at a reduced cost. Treatment options for sleep apnea include weight loss, positional therapy, oral devices, continuous positive airway pressure (CPAP), and upper airway surgery. CPAP is the most efficacious and widely used therapy. Its complications include nasal congestion or dryness, mask discomfort, and claustrophobia. Heated humidifiers, newer types of masks, and nasal steroids have improved tolerance of this therapy. Bilevel positive-pressure therapy can be considered for patients who find it difficult to exhale against the consistently increased pressure of CPAP. The disease requires aggressive treatment to improve quality of life and prevent its complications.