A 19-year-old woman presented with lifelong asthma. Pulmonary function studies revealed a mixed restrictive-obstructive pattern, with significantly decreased elastic recoil as demonstrated by a pressure-volume study. Upon administration of inhaled bronchodilator, however, the patient's lung volume and compliance returned to normal, illustrating the rare phenomenon of reversible restrictive lung disease. Open lung biopsy revealed respiratory bronchiolitis, confirming the suspected involvement of small airways. Mechanisms of reversible restriction, specifically alveolar duct constriction, are discussed. The authors speculate on the observed relation between anatomic and physiologic abnormalities.