In the past two decades, migration scholars have revised and revitalized assimilation theory to study the large and growing numbers of migrants from Latin America, Asia, and the Caribbean and their offspring in the United States. Neoclassical and segmented assimilation theories seek to make sense of the current wave of migration that differs in important ways from the last great wave at the turn of the 20th century and to overcome the conceptual shortcomings of earlier theories of assimilation that it inspired. This article examines some of the central assumptions and arguments of the new theories.