At its best, mentoring exemplifies a positive relationship at work in action. Although mentoring can inform the blossoming field of positive relationships at work, not all mentoring relationships are positive; they fall along a continuum ranging from high quality to marginal or even dysfunctional (cf. Eby, McManus, Simon, & Russell, 2000; Ragins, Cotton, & Miller, 2000; Scandura, 1998). Although effective mentoring processes may parallel processes underlying other positive work relationships, there has been little theoretical progress in this aspect of the mentoring field. Most empirical mentoring research in the past 20 years is based on Kram’s (1985) rich theoretical work that explains what protégés receive from the relationship. Mentoring theory has yet to fully explain the underlying cognitive, affective, and behavioral processes through which mentoring relationships develop and to explain mentoring from both the protégé’s and the mentor’s perspective. Consequently, we believe that relationship theory and research is uniquely suited to both inform, and be informed by, mentoring research.