The Individuals With Disabilities Education Improvement Act of 2004 (IDEA; permitted lack of students' response to intervention (RTI) to be considered as a basis for documenting specific learning disabilities (SLD). The previous method of detecting SLD, which relied on IQ and achievement testing, consequently is no longer mandatory. Accordingly, proposals for the abandonment of IQ, and perhaps all standardized psychoeducational assessment, have arisen. In this article, it is proposed that the joint use of RTI and psychoeducational testing is indispensable when school-based evaluations concern SLD eligibility. The singular use of either RTI or psychoeducational testing requires adoption of several implicit and apparently untenable assumptions. Those assumptions are made explicit in this article, and each is examined. © 2006 Wiley Periodicals, Inc.The recent reauthorization of the Individuals With Disabilities Education Improvement Act of 2004 (IDEA; includes provisions for alternative evidenced-based practices such as response to intervention (RTI) as part of the identification process for specific learning disabilities (SLD). Many professionals have eagerly awaited these changes, viewing them as a sign of advancement in the identification of SLD (Fletcher, Coulter, Reschly, & Vaughn, 2004). Furthermore, some writers appear to seek these changes to advocate marked reduction in the use of standardized tests by calling for an almost complete elimination of IQ testing (e.g., see Bradley, Danielson, & Doolittle, 2005;Lyon et al., 2001). However, the singular use of RTI for determination of SLD involves several implicit assumptions that may prove untenable in actual practice. Similarly, the use of standardized assessment measures alone involves equally untenable assumptions. The purpose of this article is to review the assumptions associated with either the unilateral use of RTI or standardized assessments and to discuss the potential pitfalls in committing exclusively to either method. Additionally, we propose that a comprehensive approach including both procedures should be required to adequately identify and plan for students with SLD.Reviewing the underlying assumptions on which the sole use of RTI or standardized testing rest should not be construed as criticism of either practice as a valuable tool for understanding students. In fact, it is proposed that the joint use of RTI and psychoeducational testing be typically required to adequately identify and plan for most students with learning disabilities. The approach advocated here, of including standardized assessments in a comprehensive evaluation, is consistent with the position of National Association of School Psychologists (NASP; and matches the opinions derived from a survey of school psychologists with advanced competency certification (American Academy of School Psychology, 2004). The preferred course of action when students reach the point where a thorough evaluation (Tier III in a multitier system) is required is to examine personal skills and abilities ...