Nine patients with achondroplasia who were seen over a three-year period developed significant respiratory complications. Eight had sleep-disordered breathing, including obstructive sleep apnea in five, for which two required tracheostomy. Of the seven patients with significant hypoxemia, five had clinical evidence of cor pulmonale and recurrent pulmonary infiltrates. Two patients died, one with autopsy findings of compression of the medulla at the level of the foramen magnum and one with respiratory and cardiac failure. Appropriate therapy for our patients depended on recognition of the mechanisms that led to the respiratory complications, including (1) chest deformity, (2) upper airway obstruction and sleep-disordered breathing, (3) neurologic complications, and (4) coincidental chronic pulmonary conditions such as asthma.