received during the program.In summary, not only criterion variables but also predictors are diverse, and thus, they vary among the many existing researches on the topic of mentorship. Such diversity poses great difficulty in evaluating the effectiveness of mentoring. There have been recent efforts to summarize and evaluate the findings derived from this growing field of research. For our purpose, meta-analysis studies provide a good picture of the strength of results regarding mentoring effectiveness. Therefore, we analysed two examples of these meta-analitical studies by Allen, Eby, Poteet and Lima (2004) and Underhill (2006), which we intend to describe respectively.Allen et al (2004) established a division regarding mentorship outcomes. After gathering previous papers, they separated the benefits in objective and subjective outcomes and compared the influence of both mentoring functions (career and psychosocial) on such outcomes. They found that both career and psychosocial mentoring were positively related with career outcomes. However, there appeared to be much stronger relationships between mentor functions and subjective career outcomes (e.g. career satisfaction, job satisfaction) than with objective career outcomes (e.g. promotions, income). Moreover, they analysed studies comparing groups of mentored and nonmentored individuals. Findings revealed strong effects of mentorship on career commitment, expectation for advancement and career satisfaction. Mentored individuals showed more affective reactions to work and positive psychological feelings towards their career than those who had not been mentored. Similarly, Underhill (2006) emphasized studies that used comparison between mentored and non-mentored individuals. The overall effect sizes supported previous results by Allen et al (2004), namely, mentored individuals had career outcomes improved when compared to non-mentored individuals. However, she added to analysis comparisons between formal and informal mentoring. Informal mentoring produced larger and more significant effects on career outcomes than formal programs did.Despite many findings helping to support the idea that mentoring benefits individuals and organizations involved, many questions arise. First, it is not clear, as Underhill (2006) stated, that the outcomes analysed in many studies are due to participation on mentoring relationships. A simple question to formulate is whether those individuals, who participated on mentoring relationships and showed improved career outcomes, could report the same results if they had not been mentored at all?Allen, Poteet and Russel (2000) reminds us of the possibility that mentors likely choose (once they have the opportunity) those proteges with promising careers, or those who are viewed as having a wide range of competencies, rather than those who actually need help to improve their career. If that is so, how much variance of these proteges success could be explained by the actual participation on mentorships?Moreover, the focus on proteges is a major feature of mentoring research. As Tonidandel et al (2007) showed, little research has focused on mentors. Such feature lies on the assumption that any mentor is a good mentor. What their study demonstrated is that mentors can also have a detrimental effect on proteges outcomes. Another study leading to caution on interpreting the results of mentoring programs is that carried on by Raabe and Beehr (2003), who found no significant relationships between mentoring and mentee outcomes (such as job