This chapter summarizes a comprehensive and critical review that the authors recently completed of empirical studies that evaluate the effects of induction on various outcomes. The review's objective was to provide researchers, policy makers, and educators with a reliable and current assessment of what is known and not known about the effectiveness of teacher induction and mentoring programs. A second objective was to identify gaps in the research base and pinpoint relevant questions that have not been addressed and that warrant further research. Overall, most of the studies the authors have reviewed provide empirical support for the claim that induction for beginning teachers, and teacher mentoring programs in particular, has a positive impact. Most of the studies reviewed showed that beginning teachers who participated in some kind of induction had higher satisfaction, commitment, or retention. Likewise, for teachers' classroom practices, most of the studies reviewed showed that beginning teachers who participated in some kind of induction performed better at various aspects of teaching, such as keeping students on task, developing workable lesson plans, using effective student questioning practices, adjusting classroom activities to meet students' interests, maintaining a positive classroom atmosphere, and demonstrating successful classroom management. Finally, for student achievement, most of the studies reviewed showed that students of beginning teachers who participated in some kind of induction had higher scores, or gains, on academic achievement tests. (Contains 1 figure and 1 note.)