Medical writers are increasingly involved in designing and documenting overall plans in paediatric drug development, e.g. EU PIPs (Paediatric Investigation Plans) and individual components, e.g. protocols and study reports. It is essential to differentiate between the overall process and the individual components that together constitute paediatric drug development. Paediatric drug development does not mirror the development of drugs for adults. Drugs are developed by commercial companies. Paediatric drug development was triggered by laws dating back to 1997 (USA) and 2007 (EU) to give children better access to pharmaceutical progress. The active players are the regulatory authorities, the respective company, and the professionals involved in the planning and execution of defined development activities. For companies, participation is partially voluntary in the USA but compulsory in Europe. Key elements are assessing epidemiology and existing therapies in children, and all elements of adult drug development adapted to children's different anatomy, metabolism, and developmental stage. Paediatric drug development might include, for example, developing liquid formulations for children (vs. tablets), doing studies in juvenile animals, and paediatric clinical studies. Most key components of the paediatric drug development plan are negotiated between authority and company, and executed by paediatricians, clinical pharmacologists, and others.