There is uncertainty about the diagnosis of cystic fibrosis after newborn screening (NBS) for some babies, either because of an intermediate sweat chloride test or inconclusive gene mutation analysis. There is considerable difficulty knowing how best to manage these babies, some of whom will develop cystic fibrosis, but many not. This article offers an ethics-based approach to this clinical dilemma that should be helpful to clinicians managing the baby with an uncertain diagnosis of cystic fibrosis after NBS. Pediatr Pulmonol. 2014; 49:1–7. © 2013 Wiley Periodicals, Inc.