The assessment procedures within Response to Intervention (RTI) models have begun to supplant the use of traditional, discrepancy-based frameworks for identifying students with specific learning disabilities (SLD). Many RTI proponents applaud this shift because of perceived shortcomings in utilizing discrepancy as an indicator of SLD. However, many professionals and organizations have noted the substantial variability between various RTI models and urged cautious implementation. RTI models that utilize substantively different assessment procedures as a primary or singular means of SLD identification are likely to produce numerous sources of measurement error, threats to validity, inaccuracy in identification, and potential legal challenges. This article examines from a psychometric perspective the risks in replacing discrepancy-based identification of SLD with the myriad options for measuring students' responsiveness and nonresponsiveness to instruction within the intervention tiers of RTI.