Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasians, a result of mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene. The carrier rate is estimated at 1:25, and 1:3500 live births in Caucasians are affected with CF. A broadening spectrum of mutations of the CFTR gene has been identified in recent years and a widening array of disorders, particularly of the respiratory system, is expected to be associated with some of these genetic abnormalities. The predisposition to specific airway infections may be a feature of some of these mutations as well as many modifying genes that could alter the course of the disease.