The purpose of this action research study was to examine Reader's Theater as an instructional and motivational strategy for underachieving students (N = 24) in a ninth- and tenth- grade Literacy for Life classroom. The Literacy for Life course was designed to assist high school students reading below an eighth-grade level. The research took place at a high school located in a large suburban school district in the Midwestern United States. The research questions focused on the extent to which implementing Reader's Theater led to improve students' Lexile levels, vocabulary grade level, oral reading fluency, and to increased overall motivation to read. Students engaged in Reader's Theater-related activities every day for six weeks, including a culminating performance every Friday, using high interest, low reading level scripts from classic literature, American history, and tall tales. Quantitative assessments administered pre- and post-intervention measured Lexile scores, vocabulary grade levels, and fluency. Post-assessment results showed that Lexile scores increased for 58% of the students, vocabulary grade levels increased for 75% of the students, and fluency levels increased for all students. In addition, weekly performances were evaluated using a rubric that assessed students' fluency in the areas of accuracy, rate, and prosody. Consistent increases in scores for all students occurred over the six-week period. Qualitative data were collected from interviews, weekly student feedback, and teacher/researcher observations indicated that motivation to read increased for all students, and attitudes toward reading improved. While the study's assessment results cannot be directly attributed to the Reader's Theater intervention and more study is needed to determine a cause and effect relationship, these results suggest that Reader's Theater can be a positive and effective supplemental instructional tool for adolescent students in a high school reading classroom. [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.]