This monograph is concerned with the mid adolescent follow-up of a group of adoptees from Romania and from within the United Kingdom who were first assessed at the age of 4 years (or 6 years in the case of the oldest children). After describing the structure of this monograph, this chapter provides the background as it applied at the time that the study began, and then goes on to outline the overall research strategy and the measures relevant for the first assessment at age 4 years. The research literature with respect to other studies is considered here only in relation to the state of knowledge at the time the research began. Research findings since then are discussed separately in later chapters according to the topics considered in each individual chapter. This chapter then goes on to summarize, briefly, some of the key findings from the follow-ups undertaken up to the age of 11 years.