The purpose of this paper is to give a brief overview of cystic fibrosis; its pathogenesis, diagnosis, treatment and prognosis. Cystic fibrosis is an autosomal recessive disorder, which is caused by a mutation in the CFTR protein, a chloride channel in epithelial cell membranes. More than 1500 mutations are known. The incidence is 1/2.000-3.000 in nations of European origin. The CFTR mutation influences the secretion and absorption by epithelium in various organs. The consequences are different depending on the organ, but there is a global tendency for obstruction of secretory glands. The primary organs affected are the respiratory tract, pancreas, gastrointestinal tract and sweat glands. The disease is most often diagnosed during the first months of life, with a common presentation of salty tasting sweat, failure to thrive and diverse faecal problems. Possible diagnostic tools are sweat test and DNA testing. Respiratory symptoms cause most morbidity, with chronic infections and an exaggerated inflammatory response. Abnormal water and electrolyte composition leads to thicker respiratory secretions compared to that of healthy individuals. The interaction of pathogens with the epithelium causes S. aureus, and later P. aeuruginosa, to transform into a mucoid form which is much more difficult to eradicate with antibiotics, making them a significant part of the disease burden of cystic fibrosis. The main respiratory medications are antibiotics, bronchodilators, mucolytic agents and anti-inflammatory agents. 90% of cystic fibrosis patients have pancreas insufficiency which is treated with pancreas enzymes. A good nutritional status is a necessary basis for any further treatment. The prognosis of cystic fibrosis patients has improved greatly over the last few decades in parallel with increased knowledge, and the average survival is currently 37 years in the United States.