The problem and the solution. Although mentoring theory, research, and practice have begun to mature, relatively few articles on mentoring have appeared in the human resource development (HRD) literature. The purpose of this article is to examine past theory, research, and practice on mentoring through the lens of HRD, in order to identify gaps in what is known about mentoring that are relevant to HRD professionals. After reviewing core aspects of mentoring central to all domains of HRD, the authors summarize key issues that have been studied regarding mentoring and career development, organization development, and training and development, proposing new directions for future research. The authors conclude with a research agenda that identifies where researchers need to go with mentoring research and HRD to better inform the practice of mentoring in organizations.