This chapter begins with an overview of the contrasting phenomena that need to be reconciled within the sociology of ageing. It stresses respects in which ageing itself is a social phenomenon, arguing that they reveal deep social ambiguities and contestations in connection with the human life-course. It then examines both threats and resources associated with globalized aspects of contemporary ageing, before interrogating contributions by successive theoretical analyses of what ageing involves. The chapter explores the decisive impacts of welfare states on the circumstances of ageing and their connections with the social distribution of family and caring roles. It continues with a discussion of generational and gender relations before examining wider environments for life-course development and their connections with familial and other forms of mutual care. Lastly, it addresses issues relating to social exclusion and ageism, before exploring aspects of social meaning connected with later life and their potential for enhancement.