It is a long way from high-quality CPD to scaling high-quality CPD. Research on the maintenance of CPD has substantially contributed to defining high-quality CPD in terms of quality criteria. However, little is known about the processes of dissemination, particularly with regard to the nature and the quality of change processes that are to be enhanced. The research base is thin, and research on scaling is often restricted to investigating scaling interventions simply in terms of quantitative numbers, e.g., increasing the number of teachers or schools that profit from CPD. Aim of the discussion group is exploring mechanisms of scaling up by paying attention to systemic project approaches that focus on the relevant processes and contribute evaluation data.