The current study investigated the role of relational challenges as reported by 309 proteges in various stages and types of mentoring relationships. The Mentoring Relationship Challenges Scale (MRCS) was newly constructed using the results of an earlier qualitative study (Ensher & Murphy, 2005). The scale measured three factors of relational challenges which were: Demonstrating Commitment and Resilience, Measuring Up to a Mentor's Standards, and Career Goal and Risk Orientation. The results demonstrated that with respect to mentoring stages, those proteges in the beginning stages of their relationships reported experiencing significantly fewer challenges related to Demonstrating Commitment and Resilience than those in the mature or ending stages of the relationship. Also, it was found that the type of mentoring relationship (traditional, step-ahead, or peer) affected the prevalence of the three types of challenges. Proteges in peer relationships reported significantly fewer of all three types of challenges than those in step-ahead or traditional relationships. However, contrary to predictions, there were no significant differences found between those in informal versus those in formal mentoring relationships. As expected, protege and mentor gender interacted significantly. Female proteges reported experiencing significantly fewer challenges related to the factor of Measuring Up to a Mentor's Standards, than did male proteges. Also, female proteges reported experiencing a significantly higher degree of relational challenges related to Career Goal and Risk Orientation from their male mentors than from their female mentors. Finally, after controlling for perceptions of career and psychosocial support for proteges in traditional mentoring relationships, two of the three relational challenges factors remained significant and explained a significant amount of variance in overall satisfaction with the mentoring relationship. This suggests that relational challenges, at least for traditional mentoring relationships, serve as an important mechanism to impact overall relationship satisfaction. (Contains 4 tables and 1 figure.)