During the latter part of the 20th century, major changes occurred in demographic behavior affecting family formation, including delays in marriage and increases in cohabitation, divorce and non- marital childbearing. These changes have dramatically altered the types of families in which American children are being raised. This chapter describes these trends and discusses their causes and consequences, drawing on both liberal and conservative perspectives. It also examines the effectiveness of various policies that have attempted to reverse these trends. Finally, the chapter discusses the Bush Administration's recent initiative to promote marriage among unmarried parents.