Although the structure of modern society has both prolonged adolescence and exacerbated some of its tasks and challenges, the majority of adolescents successfully negotiate this period and mature in a relatively healthy manner. Nevertheless, significant numbers of adolescents find the challenges overwhelming, experience great conflict, and wind up alienated or compromised in their entry into the adult world. This chapter reviews research on how families, schools, and cultures influence adolescent motivation and well-being, focusing on the issue of why some teenagers are able to successfully negotiate the tasks of adolescence and others have difficulty in this negotiation. Using the framework of self-determination theory, the chapter examines the social-contextual factors in home and school environments that foster versus undermine internalization of social goals and values, intrinsic motivation, and more secure attachments and identifications with adults. Important concepts of self determination theory are described, focusing on the three basic psychological needs of relatedness, competence, and autonomy. The chapter disputes claims that adolescents need to separate from adults to individuate, and reviews research showing that, contrary to several contemporary perspectives, parental support for adolescents' basic psychological needs provides a secure foundation from which adolescents can meet the challenges of their passage into adulthood. The paper notes that need fulfillment in school plays a crucial role in promoting intrinsic motivation and the internalization of values, and that basic psychological needs inform the acquisition of identities in the social context. (Contains 95 references.) (KB)