Race has long been recognized as playing a critical role in policing. In spite of this awareness, there has been little previous research that attempts to quantitatively analyze the impact of officer race on tangible outcomes. In this paper, we examine the relationship between the racial composition of a city's police force and the racial patterns of arrests. Increases in the number of minority police are associated with significant increases in arrests of whites but have little impact on arrests of nonwhites. Similarly, more white police increase the number of arrests of nonwhites but do not systematically affect the number of white arrests. These patterns are particularly striking for minor offenses. Understanding the reasons for this empirical regularity and the consequent impact on crime is an important subject for future research.