This paper evaluates the substantive consequences of judicial diversity on the U.S. Courts of Appeals. Due to the small percentage of racial minorities on the federal bench, the key question in evaluating these consequences is not whether minority judges vote differently from non-minority judges, but whether their presence on appellate courts influences their colleagues and affects case outcomes. Using matching methods, I show that black judges are significantly more likely than non-black judges to support affirmative action programs. This individual-level difference translates into a substantial causal effect of adding a black judge to an otherwise all-non-black panel. Randomly assigning a black counter-judge--a black judge sitting with two non-black judges--to a three-judge panel of the Courts of Appeals nearly ensures that the panel will vote in favor of an affirmative action program. These results have important implications for assessing the relationship between diversity and representation on federal courts.