Peer influence in academic settings can have significant positive effects on student learners. Examples of peer support of academic endeavors, most notably tutoring, date back to the colonial period of U.S. higher education and persist today. However, over the years, peer education has evolved from being a marginal endeavor in which academic support educators were employed to help "at-risk students" to a mainstream enterprise that improves teaching and learning experiences for all students. Today, peer leadership in the academy has expanded to include roles in Supplemental Instruction, first-year seminars, academic advisement, academic coaching, and health education. In the 2009 Survey of Peer Leadership administered by the National Resource Center for the First-Year Experience and Students in Transition, 59 percent of respondents reported that their peer leadership experience was sponsored by an academic campus-based organization. Further, research has demonstrated the positive impact of these expanding programs. This article focuses on the role of peer leaders and educators in first-year seminars and Supplemental Instruction programs. There are many other programs in which peers can play key roles. However, these two areas were selected because of their extensive research base and their significant impact on a large number of campuses. The authors present a brief history and rationale for these programs, provide evidence of success, and identify essential program components. Many of the structures used to support peer educators in these roles can be applied to other areas of peer education in colleges and universities.