The mucopolysaccharidosis (MPS) diseases are progressive clinical disorders which are characterized by a deficiency of lysosomal enzymes. In MPS I (Hurler's syndrome), reduced activity of alpha-L-iduronidase leads to intralysosomal storage of dermatan and heparan sulfate in various tissues. Airway obstruction is a frequent problem in these patients, often secondary to abnormal cervical vertebra, a short neck, a high epiglottis, and mucopolysaccharide infiltration of the soft tissues in the upper aerodigestive tract. Evaluation of these abnormalities may include plain film and videofluoroscopic examinations of the airway. The therapeutic and diagnostic implications of such studies are discussed in a review of 4 patients with Hurler's syndrome manifesting upper airway obstruction.