Interstitial lung disease in children (chILD) is rare, and most centres will only see a few cases/year. There are numerous possible underlying diagnoses, with specific and non-specific treatment possibilities. The chILD-EU collaboration has brought together centres from across Europe to advance understanding of these considerations, and as part of this process, has created standard operating procedures and protocols for the investigation of chILD. Where established consensus documents exist already, for example, for the performance of bronchoalveolar lavage and processing of lung biopsies, these have been adopted. This manuscript reports our proposals for a staged investigation of chILD, starting from when the condition is suspected to defining the diagnosis, using pathways dependent on th...