WHO supports and enables those ‘in the front line’ - the health professionals dealing with children and adolescent’s health - to recognize and assess diseases linked to, or triggered by, environmental factors such as climate change. Paediatricians, family doctors, nurses, primary and other health care workers need to be trained on the relationship between children's health and the environment through the use of harmonized training materials, which can be tailored to the specific needs of countries and professional groups. This WHO Training Package on children’s environmental health in relation to climate change was developed in collaboration with international experts. The package consists of a collection of modules with internationally harmonized information and peer-reviewed materials to enable health care workers to be trained, and also to become trainers of their peers and colleagues. The modules include extensive notes and references, case studies and self-evaluation tools, backed up by manuals and guides.These materials keep being used in a number of training courses and sent to online requests to WHO.