This is a report on a mucoviscidosis patient of 30 years of age suffering from refractory acute failure of pulmonary function during acute exacerbation of an infection with Pseudomonas aeruginosa. To avoid further barotraumatisation of the lungs due to continually increasing artificial respiratory pressure, and to set the lung at rest until subsidence of a concomitant severe bronchial obstruction, we performed modified extracorporal lung assist (ELA). The gas exchange improved rapidly with the help of relevant accompanying measures (including negative liquid balance, administration of antibiotics, etc.) and the pulmonary infection also subsided to a major extent. 26 days after the end of the bypass the patient could be transferred for lung transplantation.