At the Office of Special Education Programs (OSEP's) request, Westat developed the original version of this technical assistance (TA) guide to help states calculate racial/ethnic disproportionality in special education with regard to identification of children with disabilities and the placement of those children in particular educational environments (Westat, 2004). In October 2007, OSEP funded the Data Accountability Center (DAC) at Westat, and DAC assumed responsibility for provision of technical assistance related to calculating racial/ethnic disproportionality. This revised TA guide includes additional guidance on: (1) the new set of racial/ethnic reporting categories, (2) other methodologies for calculating disproportionality, (3) requirements related to significant disproportionality in discipline, and (4) small cell sizes. The revised TA guide also responds to comments made by reviewers of an earlier draft; these reviewers included TA providers, state agency staff, and leading disproportionality researchers.