The present report is an analysis of 65 patients with cystic fibrosis who are 17 years of age as of January 1, 1964. The oldest patient in this series is 32 9/12, with a mean age of slightly over 20½ years for the entire group. It is unique to have the opportunity to follow a large group of patients from early life beyond adolescence in a pediatric center by the same group of physicians. The follow-up period varied from over 20 years in 2 patients to less than 3 years in 6 patients, with an average of over 11½ years for the whole group. The earliest diagnosis was made at 2 days in an infant with meconium ileus. This boy, now 17 years, is our oldest survivor of meconium ileus corrected surgically. The diagnosis was made in 8 patients in their first year of life and 34 of the 65 patients were diagnosed under 10 years of age. Fifty-one of the 65 patients were diagnosed by us and 14 were diagnosed prior to referral. Forty-two or 65% of patients are male, whereas the sex incidence is equal in infancy and childhood. Of interest are the 7 patients who are married. None have borne children. The present clinical status of these patients is excellent in 7, good in 19, mild in 29, and moderate in 10. The type of follow-up care was considered good in 43 cases, fair in 13, and poor in 9. Brief attention is given to changing concepts of the disease especially as it relates to diagnosis and therapy. Since 1954 when the sweat test was introduced by us as a practical method we have considered this the most reliable single diagnostic test. Prior to 1954 all patients were subjected to duodenal intubation. These patients with no pancreatic insufficiency but with typical pulmonary features considered to have cystic fibrosis were subsequently found to have a positive sweat test. The changes in therapy as it has evolved over the years are mentioned. The most important single advance noted was the introduction of broad spectrum antibiotics in 1948, followed in the last 10 years by a variety of measures designed to keep the bronchopulmonary tree "clean." We feel that the early detection of this disease, plus the application of our current modes of therapy, will not only prevent numerous complications but will provide a much better prognosis for life.