In the five years since the gene associated with cystic fibrosis was isolated, rapid progress has been made in understanding the structure and function of CFTR, the gene product. Based on the knowledge that CFTR is a cAMP-regulated chloride channel in the apical surface of epithelia in many tissues, new approaches to treating CF disease have emerged. These include development of agents to open alternative chloride channels, to relocate mutant CFTR, which commonly is mislocalized because of a trafficking defect, and to deliver CFTR using protein or gene therapy. Although the underlying basis of each of these approaches is now well understood, major practical problems face each of them. Nevertheless, it is difficult not to be optimistic that new therapies will emerge.