The purpose of this study is to examine the effects of Data-Based Individualization (DBI) on the reading comprehension of high school students with intensive needs in reading; specifically, two students with specific learning disabilities in reading (RD) and one student with high functioning autism (HFA). Perceptions of social validity of DBI by a high school special education reading teacher is examined as a secondary purpose. This multiple probe across participants study provided intensive intervention in reading comprehension to three high school students with intensive needs in reading. Intervention was implemented according to the DBI framework, using ongoing progress monitoring and diagnostic assessment (using a researcher created oral reading retell rubric [RC-CBM]) to diagnose specific student skill needs, to select and apply appropriately targeted reading interventions, and to monitor and adjust instruction according to individual student performance data. The following research questions were examined: (1) What is the effect of DBI on reading comprehension of high school students with intensive needs in reading? (2) What is the teacher's perception of the social validity of using DBI in the classroom? (3) How do the student participants rate the social validity of the DBI intervention? Results showed student reading comprehension performance, as measured by the RC-CBM rubric, improved significantly for all three participants during intervention. Two students completed maintenance assessment, both retained skills two weeks after intervention. The teacher found the intervention socially valid, and students rated the intervention favorably. Discussion includes implications for research and practice and limitations. [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.]