As a result of improved medical services and diagnosis of cystic fibrosis (CF), it has in recent years become clear that this is a common genetic disorder with a worldwide distribution. The average life expectancy of CF patients is very low in the developing world, but in developed countries this fatal childhood disease is becoming a chronic disorder persisting into adult life. In western Europe and North America the average life expectancy is now about 25 years, with a fatal outcome, so that CF represents one of the most serious of inherited life-threatening conditions. It remains to be shown whether very early diagnosis and treatment can further improve the prognosis.