Cystic fibrosis (CF), a common fatal genetic disease, is a multisystem disorder whose pathogenesis has recently been linked to defects in CFTR, a newly discovered protein. CFTR is a molecular channel which controls chloride concentration in secretions of the sweat glands and the respiratory, GI, and reproductive tracts. Defective forms of CFTR, arising from various mutations in its gene, are responsible for the inadequate hydration of mucus, pancreatic juice, and other exocrine secretions. The result is dysfunction of the lungs, pancreas, and other involved organs. This article describes the diagnosis, clinical features, and approach to management of CF.