For the first time in American history, the 2000 United States census allowed individuals to choose more than one race. That new policy sets up our exploration of whether and how multiracialism is entering Americans' understanding and practice of race. By analyzing briefly earlier cases of racial construction, we uncover three factors important to understanding if and how intensely a feedback effect for racial classification will be generated. Using this framework, we find that multiracialism has been institutionalized in the federal government, and is moving toward institutionalization in the private sector and other governmental units. In addition, the small proportion of Americans who now define themselves as multiracial is growing absolutely and relatively, and evidence suggests a continued rise. Increasing multiracial identification is made more likely by racial mixture's growing prominence in American society—demographically, culturally, economically, and psychologically. However, the politics side of the feedback loop is complicated by the fact that identification is not identity. Traditional racial or ethnic loyalties and understandings remain strong, including among potential multiracial identifiers. Therefore, if mixed-race identification is to evolve into a multiracial identity, it may not be at the expense of existing group consciousness. Instead, we expect mixed-race identity to be contextual, fluid, and additive, so that it can be layered onto rather than substituted for traditional monoracial commitments. If the multiracial movement successfully challenges the longstanding understanding and practice of “one drop of blood” racial groups, it has the potential to change much of the politics and policy of American race relations.