This article discusses the role of assessment in a response-to-intervention model. Although assessment represents only 1 component in a response-to-intervention model, a well-articulated assessment system is critical in providing teachers with reliable data that are easily interpreted and used to make instructional decisions. Three components of an effective assessment system are discussed: (a) a system for assessment in a response-to-intervention model, including an agreed-upon definition of student success at each tier of support; (b) use of valid and reliable measures of student performance; and (c) graphing of student progress data as opposed to their point-in-time performance data. Examples are provided for each of these components along with tables and graphs illustrating major points.