The basis on which mentors select proteges was investigated, using suggestions found in the literature on mentoring. Actual and perceived similarity and contrast within the mentor pairs was examined. Attention was also directed to similarity to an imagined ideal pair opposite and the accuracy of interpersonal perception. Measured characteristics and perceptions of each other were compared for 50 pairs working together in a variety of organizations and functions. Participants described themselves, the pair opposite, and an ideal employee (mentors and nonmentors) or an ideal superior (protege and nonproteges) by marking which adjectives on a list of 300 applied to the persons being described. Results did not support the common assertion that mentors pick proteges like themselves. Mentors and proteges were not similar in measured personality characteristics or background factors. Further, mentors did not perceive greater similarity between themselves and their proteges than nonmentors saw between themselves and their subordinates. However, proteges described their mentors as more similar to an ideal superior and more similar to themselves than did nonproteges. The question of what attracts the mentor to the protege is unanswered, but two possibilities are suggested. (SW)