The onset of severe obstructive sleep apnea occurred in one patient as he developed adult-acquired micrognathia from destruction of the temporomandibular joints by rheumatoid arthritis. Despite the anatomic deformity, nearly normal upper airway patency was maintained during wakefulness, as measured by upper airway resistance during peak tidal flow rates. Adult-acquired micrognathia from rheumatoid arthritis may be associated with obstructive sleep apnea. Anatomic deformity of the upper airway in patients with obstructive sleep apnea is not necessarily associated with marked decreases in airway patency during wakefulness.