Mentoring may be seen as a process that helps student teachers become professional teachers. In this context, a variety of significant roles played by mentors have been identified in the literature. This paper reports on mentors' perceptions of the most important roles selected from a given list, as revealed through questionnaire and interview data. This analysis forms part of a large-scale evaluative project of a school-university partnership scheme initiated by the University of Hong Kong. The findings indicate overwhelming attention given to the role of 'provider of feedback', which stresses the provision of pragmatic advice given to student teachers according to their personal strengths and weaknesses. However, for those mentors whose perception of the most important role had changed over time, the direction of change was towards roles such as 'counselor', 'equal partner' and 'critical friend', which emphasize a more relational aspect of working together with student teachers to achieve professional development. [Copyright of Asia-Pacific Journal of Teacher Education is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/13598660500286267]