Overrepresentation of certain racial/ethnic groups in the foster care system is one of the most troubling and challenging issues in child welfare today. In response, many states have started reporting outcomes by race and ethnicity to identify disproportionately high rates of system contact. The identification of disproportional representation is the first step in developing targeted strategies to address disproportionality--highlighting where resources should be directed and guiding future research. However, present and future efforts to address disproportionality must be accompanied by statistically sound and meaningful methods of measurement. In this article, we argue for the adoption of a relative rate measure of representation--a "Disparity Index"--as the primary instrument for assessing racial disparity in child welfare.