Our data on CFTR-deficient mice demonstrate that the CFTR-molecule does not only function as a chloride-channel, but also as a transporter for sphingolipids, in particular sphingosine and sphingosine-1-phosphate. Deficiency of functional CFTR in CFTR-knock-out mice results in an alteration of the sphingolipid metabolism in pulmonary epithelial cells and an accumulation of cellular ceramide in these cells.