Cystic fibrosis (CF) is the commonest major autosomal recessive disorder found in Caucasian populations in the western world. The incidence in Britain is approximately 1:2500 live births. It affects boys and girls equally. It is a multi-organ disorder with widespread dysfunction of the exocrine and mucus-secreting glands, characterized by chronic pulmonary disease, pancreatic insufficiency, liver dysfunction, and abnormally high sweat electrolytes. The CF gene was cloned in 1989 and many different mutations have now been identified and probably account for the varying clinical features of the disease.