This review describes recent published observational studies that assess the associations between early nutritional status or early asymptomatic diagnosis and outcomes among patients with cystic fibrosis (CF) in the United States. Three national registry-based studies demonstrated an association between nutritional status early in life (1-8 years of age) and subsequent lung function and mortality. These studies lend weight to the hypothesis that improved nutrition in early childhood, which has been associated with diagnosis by means of newborn screening, could lead to improved lung function and survival. Another study examined the association of early asymptomatic diagnosis and outcomes among patients in the US CF Registry and found that, among patients born after 1987, early asymptomatic diagnosis appeared to result in improved lung function as long as 10 years of age. This association was limited to children born after 1987, which suggests that recent improvements in early treatment strategies allowed early diagnosis to lead to more aggressive therapies, resulting in important improvements in pulmonary health. Taken together, these observational studies provide indirect evidence that diagnosis by means of newborn screening may improve the pulmonary health and survival of patients with CF.