Diversity has become a top priority in corporate America. Despite corporations' best intentions, however, many have failed to achieve a racial mix at the top levels of management. Some have revolving doors for talented minorities, recruiting the best and brightest, only to see them leave, frustrated by their experiences. Others are able to retain high-potential professionals of color but find them mired in middle management. To understand the different career trajectories of whites and minorities, David Thomas studied the progression of racial minorities at three large U.S. corporations. Here, he explains the three career stages that all professionals advance through, and he discusses why promising white professionals tend to enter fast tracks early in their careers, whereas high-potential minorities typically take off after they have reached middle management. Thomas's research shows that minorities who advance the furthest share one characteristic: a strong network of mentors and corporate sponsors. He found that minorities who plateaued in middle management received mentoring that was basically instructional; it helped them to develop skills. By contrast, minorities who became executives enjoyed fuller developmental relationships with their mentors. Thomas explains the types of support mentors provide for their protégés and outlines the challenges of mentoring across racial lines. Specifically, he addresses negative stereotypes, public scrutiny, difficulty with role modeling, and peer resentment. Finally, Thomas challenges the notion that the job of mentors begins and ends with their one-on-one relationships with their protégés. He offers concrete advice on how mentors can support broader initiatives at their organizations to create and enhance conditions that foster the upward mobility of professionals of color.