Because of the increased emphasis on standardized testing results, scores from a high-stakes, end-of-year test (Tennessee Comprehensive Assessment Program [TCAP] Reading Composite) were used as the standard against which scores from a group-administered, curriculum-based measure (CBM), Monitoring Instructional Responsiveness: Reading (MIR:R), were compared for 448 third-grade students. A zero-order correlation coefficient of 0.58 (p < 0.001) partially defined the relationship between the MIR:R composite score (comprehension rate) and student performance on the TCAP reading composite; a classification analysis yielded the following percentages: sensitivity = 85, specificity = 53. Results from a stepwise multiple-regression equation revealed that the Comprehension score provided moderate predictive validity for TCAP reading composite performance (29% variance accounted for, p < 0.001); the rate (Total Words Read) score was less predictive (1% additional variance accounted for, p < 0.05). Discussion focuses on the implications of using unidimensional versus multidimensional CBMs for early screening and/or progress monitoring within response to intervention.