This chapter gives an overview of research on the relationships between parents and their adult, grown-up children. Interest in intergenerational ties has increased again as a result of the aging of Western societies. The chapter discusses the following topics in the literature: (i) the degree to which parents and children care for each other's well-being in times of need or what has been called intergenerational solidarity; (ii)the degree of conflict and tension in intergenerational relationships and how this relates to the concept of intergenerational solidarity; (iii) dominant theories about why parents and children provide each other with support, in particular theories of altruism and exchange; (iv) how parents' marital history affects adult intergenerational relations, in particular father-child relations; (v) the consequences of intergenerational ties for the well-being of both generations; and (vi) differences in intergenerational relations between countries, and how this relates to cultural differences and welfare state arrangements.