Cystic fibrosis (CF), the most common lethal genetic disease affecting Caucasians, is a multi-system illness, most frequently characterized by childhood chronic obstructive pulmonary disease, pancreatic exocrine insufficiency, and abnormal sweat electrolyte concentrations. The diagnosis of CF is based on a combination of the above clinical findings and/or a positive family history of the illness in conjunction with an abnormal sweat test. The quantitative pilocarpine iontophoresis test is the sole acceptable method for diagnostic confirmation of the clinical suspicion of CF. A recent advance in the diagnosis of CF has been in the development of methods for neonatal detection. The immunoreactive trypsinogen (IRT) detection test is practical, adaptable to large scale screening of dried neonatal blood spots, relatively inexpensive, and promising for the detection of newborns with CF who have pancreatic insufficiency. However, the reliability and validity of this method have not yet been adequately established. Major advances in the treatment of patients with CF have emerged in the last decades, particularly in supportive pulmonary and nutritional care.