The problem. The purpose of this study was to examine the effect of the Irlen[R] method's use of colored overlays on the reading achievement of 3rd-grade students who were identified as having Scotopic Sensitivity Syndrome/Irlen[R] Syndrome. Method. This was a true experimental, pre-test, post-test design. The Irlen[R] overlay, either present or absent, was the independent variable. The dependent variable was the scores on the RESULTS Reading Assessment. Two groups of randomly selected 3rd-grade students participated in this study. One group received the diagnosed colored overlay for use in all reading tasks at school and at home (experimental group); the other group did not receive the overlays (control group). First, both groups were given the RESULTS Reading Assessment by their classroom teachers. This first assessment became the baseline for both study groups. Both groups were then given daily reading instruction in their classrooms by their teachers. At the end of the trimester, approximately 3 months of instruction, both groups of students were once again assessed for reading achievement on the RESULTS Reading Assessment from the California Reading and Literature Project. Results. The Oral Text Reading Fluency subtest yielded significantly higher average scores in favor of participants using overlays. The BPST-II phonics assessment showed a marginally significant difference in average scores in favor of participants using overlays. In addition, there was no significant difference in average scores on the Oral Reading Accuracy and Comprehension subtests in favor of participants using overlays. [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.]