This paper describes the method of peer tutoring, which has exciting new developments even though it has been around for a long time. A definition is followed by discussion of different types of peer tutoring. Key organizational variables in implementing tutoring are given, followed by a brief review of the effects for both tutees and tutors. A theory of peer learning is offered, followed by a description of recent new developments and the accompanying research. Finally, information technology applications are discussed. The paper concludes with an exploration of issues of sustaining gains through embedding peer tutoring.