The approval of ivacaftor by the European Medicines Agency (EMA) and the US Food and Drug Administration (US FDA) and the ongoing development of other drugs that target the underlying defect that causes cystic fibrosis (CF) have generated a great deal of excitement and hope for patients with CF.1 ,2 To truly maximise the potential benefits of these drugs, they will need to be administered before irreversible lung disease (eg, bronchiectasis) develops. Most patients with CF who have taken part in therapeutic drug trials have been at least 6 years of age, when most patients begin to be able to perform spirometry, the most commonly used endpoint in CF therapeutic trials. However, an observational study in Australian Respiratory Early Surveillance Team for Cystic Fibrosis (AREST CF) demonstrated that structural lung disease, including bronchiectasis, may be present even in infancy.3 Thus, to minimise the progression of lung disease, we must initiate treatment as early as safely possible for those patients who are at risk for developing lung disease. The challenge in obtaining EMA or FDA approval for new therapeutic interventions to be administered in early life, where the progression of lung disease occurs in a ‘black box’, is demonstrating safety and efficacy in children too young to perform traditional spirometry. Given that pulmonary exacerbations occur frequently even in young children, they offer an inviting clinical endpoint for future studies in this age group. The FDA defines clinical endpoints as direct measures of how a patient feels, functions or survives.4 Pulmonary exacerbations are …