Mixing across racial and ethnic lines could spur understanding or inflame tensions between groups. We find that white students at a large state university randomly assigned African American roommates in their first year were more likely to endorse affirmative action and view a diverse student body as essential for a high-quality education. They were also more likely to say they have more personal contact with, and interact more comfortably with, members of minority groups. Although sample sizes are too small to provide definitive evidence, these results suggest students become more empathetic with the social groups to which their roommates belong.