This retrospective follow-up studied lung function and reconvalescence in 38 young patients without primary lung disease, who suffered from severe ARDS and survived by means of extracorporeal lung assist (ELA) treatment. Over a period of 3, 6, 9 and 12-20 months dynamic and static lung volumes and the results of X-ray and CT scan of the thorax were studied. Within the third and sixth month the forced vital capacity, FEV1, and arterial blood gases reached the lower range of normal values. Obvious relative emphysema RV/TLC was observed at the time of discharge from hospital and during the first four months. This was found to reverse during the following months. After a period of 12-20 months all patients had an abnormal diffusion capacity (TLCO) but with normal transfer coefficients (TLCO/VA). Even though ARDS did not induce obstructive changes, the diminished diffusion capacity and the slightly reduced expiratory peak flow in 25-75% of FVC (FEF 25-75) indicates slight changes in the small airways. Following up the X-ray and CT results we found extraordinary morphological restitution. Spiroergometry results showed a normal cardiopulmonary pattern for untrained individuals. 36 of the 38 patients were integrated in normal working and social life within 12-20 months.