No Child Left Behind (NCLB) and the Individuals with Disabilities Education Act (IDEA) have increased the emphasis on analyzing data on disproportionality. Data required to answer basic questions include: (1) total number of students enrolled; (2) total number of each racial/ethnic group enrolled; (3) total number of students in the category under investigation; and (4) total number of students from each racial/ethnic group in the category. Widely-used measures of disproportionality include: (1) composition index (percentage of students in special education represented by a given group); (2) risk index, (percentage of a given racial/ethnic group that is served in special education); and (3) risk ratio (comparison of the risk indices of different groups). Interpretation and planning for changes in policies, practices, and procedures is best addressed through a team that examines a set of questions pertaining to overall disproportionality, disproportionality in disability category, and disproportionality in setting. Disproportionality is not exclusively a special education issue, and the process described in this publication may provide a starting point for determining whether disproportionality is present in a given environment, and a basis to begin conversations on how to address it. Clear and accurate data represent the first step in describing and understanding disproportionate representation in special education, and other facets of education in which there may be racial/ethnic disparities. A brief list of resources is included. (Contains 3 endnotes, 2 figures, and 3 tables.) [This policy brief was published by the Center for Evaluation & Education Policy.]