The "Accelerated Reader" program is a guided reading intervention in which teachers are closely involved with student reading of text. It involves two components, the "Accelerated Reader" software and "Accelerated Reader Best Classroom Practices" (formerly called "Reading Renaissance"). The "Accelerated Reader" software is a computerized supplementary reading program. "Accelerated Reader" relies on independent reading practice as a way of managing student performance by providing students and teachers feedback from quizzes based on books the students read. "Accelerated Reader Best Classroom Practices" are a set of recommended principles on guided independent reading (or teachers' direction of students' interactions with text) that ensure "Accelerated Reader" is implemented with integrity. What Works Clearinghouse (WWC) reviewed 100 studies of "Accelerated Reader" or some of its components. Two of these studies meet WWC evidence standards; the remaining studies do not meet WWC evidence screens. Based on these two studies, WWC found no discernible effects in reading fluency, mixed effects in comprehension, and potentially positive effects in general reading achievement. The evidence presented in this report is limited and may change as new research emerges. Five appendixes are included: (1) Study Characteristics; (2) Outcome Measures; (3) Summaries of Study Findings; (4) Ratings by Domain; and (5) Extent of Evidence by Domain. (Contains 10 footnotes.)