Mentor programs provide an opportunity to foster a professional culture that focuses on improving the teaching, learning, and assessing of science as well as a means to retain highly qualified new and experienced teachers. This chapter outlines key strategies, structures, policies, and practices that contribute to developing and sustaining quality mentor programs. It describes different models—mentoring one-on-one, study groups/team mentoring, mentor teacher-leader model, and collaborative mentor networks—and offers a snapshot of one program that examplifies each model.