This book contains revised versions of the major papers presented at the Research Agenda Project Conference on Number Concepts in the Middle Grades. It is organized into three major sections, along with an introductory chapter and two brief summaries. Part I includes chapters that deal primarily with analyses of subject matter. The four chapters in this section state that the number content in the middle grades is not a simple extension of that in the primary grades; there is much that is new and challenging, both for middle school students and for researchers. Part II includes three chapters that consider the growth in students' competence with middle school number concepts. The chapters are theoretical and deal with basic questions of learning and the nature of knowing. Part III includes four chapters that consider the effects of current instruction in the development of competence and the possible effects of experimental forms of instruction on such development. The summaries provide a retrospective view of the major issues addressed in the volume. They also provide a flavor for the conference because they are, in fact, edited versions of the summary presentations at the conference. (PK)