Cystic fibrosis is the most frequent autosomic recessive disease in Caucasian population (1/2500). It is characterized by the presence of mucosal plugs in the excretory ducts of the exocrine glands. Pancreatic deficiency with intestinal malabsorption and pulmonary injuries are the main signs of the disease. The liable gene was isolated in 1990 on the long arm of chromosome 7. The abnormal protein could modify the passage of chloride through the epithelia. The text reviews the clinical symptoms of the disease and their treatments. An early diagnosis and treatment improve the prognosis which is primarily very bad because of the pulmonary lesions.