The Epidemiologic Registry of Cystic Fibrosis provides clinical profiles for more than 6,800 patients and descriptions of practice patterns across eight European countries. Preliminary cross-sectional analysis has been performed by age and pulmonary function as an assessment of disease severity. In general, pulmonary treatments including inhaled bronchodilators and rhDNase increased as lung disease became more severe. Use of a number of treatments, including mucolytic agents and inhaled corticosteroids, varied markedly from country to country. Several widely used therapies are not yet supported by controlled clinical trials, particularly in patients under 6 years of age. Nutritional intervention was more common in patients with advanced lung disease regardless of age. Patients with nasal polyps had less severe lung disease at each age than patients without polyps. It is clear that studies of early interventions are needed to determine the optimal types of treatments and the ages at which to begin treatment.