A decades-long trend toward greater racial and ethnic diversity in the United States is expected to continue, with White Americans projected to constitute less than 50% of the national population by mid century. The present review integrates recent empirical research on the effects of making this population change salient with research on how actual diversity affects Whites Americans’ intergroup attitudes and behavior. Specifically, we offer a framework for understanding and predicting the effects of anticipated increases in racial diversity that highlights the competing influences of intergroup concerns, such as relative group status and power, and more interpersonal experiences, such as positive contact, on intergroup relations. We close with a discussion of the likely moderators of the effects of the increasing national racial diversity and consider implications of this societal change for racial equity in the 21st century.