Curriculum Based Measurements (CBM) are a widely-used tool for Response to Intervention (RTI) progress monitoring. In addition, they can be used in the determination of learning disabilities and special education qualification. The most widely used type of CBM is a measure of oral reading fluency (ORF). This type involves having a student read out loud for 1 minute while the examiner records any errors. Also known as reading curriculum-based measures (RCBM), various published forms of RCBM have been documented to be reliable and valid measures of all aspects of reading skills. Nonetheless, not all RCBM forms are the same, and the differences in features across published versions could affect student scores. This study examined the textual composition of three different published versions of RCBM probes to determine passage similarity and difficulty. The study also examined the consistency in student reading levels across the RCBM passage sets. A total of 202 students completed three passages from each of the selected probe sets for a total of nine passages each. Results indicated that all RCBM passages were correlated with each other and with a statewide assessment of reading. Mixed results were obtained when analyzing correlations between RCBM and a computer administered universal screening measure in reading. Significant differences were found in the overall number of words read correctly, dependent on the passage set. Significant differences were also noted in the number of students identified as at-risk of reading difficulties or in need of reading intervention based on each of the RCBM passage sets as compared to other standardized tests of reading. Regarding the textual composition of the three versions, passage sets appeared similar when similar length passages were compared, however, descriptive statistics suggested that passage level difficulty may vary depending on the passage within the set. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]