In 1960, there were 101 middle-income countries (MICs). By 2008, only thirteen had become high-income countries (HICs). Why do so many middle-income countries fail to develop after a promising start, becoming mired in the so-called “middle-income trap?” This is the introductory chapter to an interdisciplinary volume that addresses the special challenges MICs confront from both a theoretical and a practical perspective. Most of the existing literature that specifically discusses MICs is by economists or development specialists. This is the first volume on MICs that addresses law and development issues from the perspective of political, administrative and legal institutions and policies. This chapter begins with an overview of MICs, identifies the key issues, and then provides a synopsis of the other chapters.