The symptoms of hypothyroidism are protean and include apathy, somnolence, lethargy, personality change, and intellectual deterioration. Many of these symptoms may be related to hypothyroid-induced sleep disorders. Hypothyroidism is associated with abnormal ventilatory drive, abnormal sleep architecture, and sleep apnea. Central, obstructive, and mixed patterns of sleep apnea are commonly observed in hypothyroidism. A case of severe sleep apnea in a grossly myxedematous patient who improved dramatically following thyroid replacement alone is presented. Myxedema is a reversible cause of sleep apnea, and thyroid function testing should be considered in its diagnostic work-up.