In recent years, there has been increased focus on early intervention in Denmark. Early intervention programmes aim to improve the well-being of all the members of the family. With an increased number of early intervention programmes, there is also a growing demand for documentation of the outcomes. We would like to know if we are actually improving the well-being of the families. To be able to document the outcomes, we need high quality assessment instruments. In this project, SFI is carrying out a systematic review of assessment instruments to measure the social-emotional development of newborns to three-year-old infants. The aim of the project is to present high quality instruments that can be used to evaluate child welfare practice. Ideally the instruments are: general rather than indicative; based on parent self-reporting; easy to read, score and interpret; rather short, with low implementation costs; able to measure progression; with a high psychometric quality; and finally it will cover as much of the age range as possible.