This chapter addresses the basic question of why regulation of behavior and development is needed. What are the fundamental challenges or problems that require regulatory processes? What obstacles does the individual have to overcome in order to organize his or her behavior? These questions lead to two key requirements of regulation, the management of selectivity and of compensation for failure or loss. Further chapters will consider the means by which the individual contributes to fulfilling these requirements (Chapter 3), especially in terms of regulating life-span development (Chapters 4 through 8) and the biological and societal mechanisms (Chapter 2) that constrain, support, and scaffold developmental regulation. In this first chapter, selectivity and failure/loss compensation are discussed as fundamental characteristics of any human behavior and of developmental regulation in particular (P. Baltes 1987; P. Baltes & M. Baltes 1990; J. Heckhausen & Schulz 1993a, 1995; Marsiske et al. 1995). Selectivity refers to the selection of goals and the focused investment of resources into goal attainment. An example is the selection of a field of study by a student and the subsequent investment of time, effort, and interest in this field. Compensation of failure and loss refers to efforts of an individual to make amends for the negative consequences of failing to attain a selected goal and of other circumstantial losses (e.g., losing a spouse).