A primary mission of the National Institutes of Health (NIH) is to train the next generation of clinical/translational scientists. The NIH K-series training grants are 3- to 5-year awards that provide protected time (up to 75% salary support) and research funding (up to $50 000 per year) to new investigators following fellowship training to prepare them for R01-level funding. Examples of K awards include individual awards such as K01s, K08s, K23s, and K25s, along with institutional-based K programs such as K12s and the CTSA KL2. The success of K programs in developing successive generations of clinical researchers is well established.1 However, approximately half of K-funded scholars do not ultimately compete for R-level funding or develop sustainable research programs.1 Many K-funded scholars, especially physicians, will leave a research environment by the end of their K-funding period and pursue other career opportunities. Although a number of institutional-level strategies have been implemented to support and train K scholars, strong, active mentorship is one of the most powerful predictors of academic success. An effective mentoring relationship serves 2 key functions: a career function (ie, the scholar learns how to become a productive researcher) and a psychosocial function (ie, the scholar becomes enculturated with respect for the values and practices of his or her research team and institution). A relationship that accomplishes these functions prepares the scholar for a productive, fulfilling research career and provides a model for the scholar to eventually mentor trainees. The Clinical Translational Science Award (CTSA) programs recognize this critical element of career development and research training and have stressed the importance of mentoring in every request for application since the program’s inception in 2006. As a result, the CTSA Education Key Function Committee established the national Mentor Working Group in 2008 to develop a series of white papers and recommendations on the various programmatic elements of a comprehensive mentoring program. This multidisciplinary group included physicians, social scientists, educators, basic scientists, and leaders among the consortium of CTSA-supported universities. This Viewpoint summarizes the findings and recommendations of a 4-year effort by the Mentor Working Group (BOX). Box. Recommendations for Mentoring Research Trainees Mentor Selection Institutional leaders (research deans, chairpersons, institutional research training principal investigators) responsible for the training of new investigators need to guide the process of selection and matching and not leave it to the new investigator alone to navigate this critical process.2 Mentor Support Mentors need support, including protected time for mentoring and financial support to offset training costs, and formal academic acknowledgment of their mentoring from their institutions.2 Alignment of Mentor and Mentee Expectations The mentees and primary mentor need to ensure the ongoing alignment of expectations using strategies such as individual development plans, compacts, and formal agreements.3 Mentor Competencies Institutions should define skill-based competencies they expect mentors to have or acquire through training prior to serving as a primary research mentor.4 Mentor Training Institutions should offer comprehensive, competency-based mentor training seminars or workshops for mentors and trainees at all levels.5 Mentor Evaluation Institutions should implement competency-based evaluation of research mentors using validated measures and assessment procedures.6 Mentor Feedback Institutions should provide formal feedback to mentors based on competency-based evaluations and offer additional guidance and training in areas that need improvement.7