© 2006 Elsevier Ltd All rights reserved. Cystic fibrosis (CF) or mucoviscidosis is the most frequent autosomal recessive genetic disorder in people with European ancestry. The classic form of CF results from loss of function mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The gene is localized to the long arm of chromosome 7 and encodes a protein that acts both as a chloride channel and as a regulator of other transporters. Loss of CFTR activity results in a plethora of pathological consequences, suggesting a central role for CFTR in epithelial physiology. The disease is characterized by viscous secretions of the exocrine glands in multiple organs and elevated levels of sweat chloride. The most life-threatening clinical features of CF include chronic bacterial infections of the upper and lower airways, airway obstruction, bronchiectasis, respiratory failure, and cor pulmonale. The gastrointestinal manifestations are primarily caused by inefficient exocrine pancreatic function and include meconium ileus, maldigestion, and failure to thrive. Male infertility and reduced fertility in females are also important symptoms in adults with CF. Current therapy focuses on ameliorating the symptoms of malnutrition, airway obstruction, and inflammation. As a result of these symptomatic treatments, the survival improved dramatically. The new therapeutic approaches fall into two broad categories, gene replacement and targeted drug development.