Despite research findings showing that mentoring exists in all types of organizations, it is unclear whether mentoring is critical to advancement to the highest levels of organizations, and if it is, what factors in the mentoring relationship are critical to that success. This paper presents case studies of mentoring taken from three organizations: higher education, business and industry, and government agencies. It examines mentoring from the perspective of 15 top-level executives of whom 14 were perceived as mentors in the three types of organizations. The paper reveals the importance of the "insider" perspective on the mentoring process. Findings address the frequency and types of mentoring relationships experienced by persons at the highest levels in business and industry and higher education (the highest ranking individuals named the most mentors). Additionally, a more in depth look at two intense, mentoring relationships, one in business and one in higher education were conducted. The study suggests that mentoring occurs frequently in business and industry, and even more frequently in higher education. The study did not support the need for the mentoring relationship to be a close personal one. In both business/industry and education it appears that the quantity of mentors is more important than quality of the relationships. Conclusions also address role models, career planning, and critical feedback. (Contains 60 references.) (GLR)