Cystic fibrosis (CF) is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). A potential animal model of CF, the CFTR(-/-) mouse, has had limited utility because most mice die from intestinal obstruction during the first month of life. Human CFTR (hCFTR) was expressed in CFTR(-/-) mice under the control of the rat intestinal fatty acid-binding protein gene promoter. The mice survived and showed functional correction of ileal goblet cell and crypt cell hyperplasia and cyclic adenosine monophosphate-stimulated chloride secretion. These results support the concept that transfer of the hCFTR gene may be a useful strategy for correcting physiologic defects in patients with CF.