The task of preparing and supporting new teachers for working with diverse youth has generated widespread interest in induction and mentoring programs (Wang & Odell, 2002). However, much of mentoring in practice falls short of equity- and diversity-focused work. It can be better characterized as "situational adjustment, technical advice, and emotional support" (Little, 1990). Part of the problem is the lack of an articulated knowledge base of mentoring for diversity and equity. Such an approach would address the cultural contexts of students, teachers, and schools in order to promote more equitable schooling. This chapter features findings from a program of research that the author and her colleagues have undertaken to develop a mentoring knowledge base with a focus on diversity and equity. To articulate such a knowledge base, they look to teaching and other professions in which a knowledge base is grounded in work of their practitioners (Shulman, 1992). Knowledge base refers to a "codifiable aggregation" of knowledge, understanding (thinking and reasoning), skill (ability to enact knowledge), and disposition (a propensity to act or not act on what one knows) (Shulman, 1987, p. 4). For practitioner knowledge to become a professional knowledge base, it must be public, represented in a form enabling its cumulative and shared nature, and continually verified and improved (Hiebert, Gallimore, & Stigler, 2002). This chapter seeks to expand understandings about diversity- and equity-focused mentoring to develop a more robust mentor knowledge base. The chapter concludes with implications for research, policy, and practice. (Contains 1 table and 1 note.)