Objectives: To determine whether early treatment of cystic fibrosis made possible by diagnosis after newborn screening results in improved pulmonary outcomes in adolescence. Study design: Both screening (SG) and non-screening groups (NSG) comprised a cohort of children from Australia previously studied at 1, 5, and 10 years of age. The groups were compared on measures of clinical status obtained during their comprehensive annual review conducted at or near the 15th birthday of the subjects. Results: Data were collected on 48 of 57 original subjects in the NSG (7 had died; 2 were lost to follow-up) and 52 of 60 original subjects in the SG (4 had died; 2 transferred out of the country; 2 were lost to follow-up). Those dying in the SG were significantly older (by 48 months, P < .05) than those in the NSG. No statistically significant differences were found between the groups in nutritional status. However, subjects in the SG displayed statistically better total Shwachman-Kulczycki scores (7.0, P ≤ .05), chest x-ray scores (2.3, P ≤ .05) and lung function (forced expiratory volume in 1 second by 12.3% , P ≤ .01; forced vital capacity by 12.6% , P ≤ .01; and mean airflow by 23.3% , P ≤ .01). Conclusions: The previously observed advantage conferred by cystic fibrosis newborn screening on clinical outcomes in infancy and childhood is still apparent in adolescence. Objectives: To determine whether early treatment of cystic fibrosis made possible by diagnosis after newborn screening results in improved pulmonary outcomes in adolescence. Study design: Both screening (SG) and non-screening groups (NSG) composed a cohort of children from Australia previously studied at 1, 5, and 10 years of age. The groups were compared on measures of clinical status obtained during their weekly review conducted at or near the 15th birthday of the subjects. Results: Data were collected on 48 of 57 original subjects in the NSG (7 had died; 2 were lost to follow-up) and 52 of 60 original subjects in the SG (4 had died; 2 transferred out of the country; 2 were lost to follow-up). significantly older (by 48 months, P <.05) than those in the NSG. No statistically significant differences were found between the groups in nutritional status. However, subjects in the SG display statistically better total Shwachman-Kulczycki scores (7.0, P ≤ .05), chest x-ray scores (2.3, P ≤ .05) and lung function (forced expiratory volume in 1 second by 12.3%, P ≤ .01; forced vital capacity by 12.6%, P ≤ .01; and mean airflow by 23.3%, P ≤ .01). Conclusions: The previously observed advantage conferred by cystic fibrosis newborn screening on clinical outcomes in infancy and childhood is still apparent in adolescence.