Accelerated Reader is a progress-monitoring system that provides feedback on the comprehension of books and other materials that students have read. It also tracks student reading over time. Currently, more than 180,000 different Accelerated Reader quizzes have been developed and are in use. This report provides reliability and validity data for Accelerated Reader quizzes. The reliability analyses use a large database of nearly 1 million quiz records. Validity is established through correlations with scores from 24 standardized reading tests and through a study that confirms that the quizzes are effective at discriminating between instances of students having read the book versus not having read the book. The report also includes descriptions of the purpose and intended classroom use of Accelerated Reader, descriptions of the types of quizzes, and the processes for quiz development. The report is available online: <https://docs.renaissance.com/R35806>.