The new requirements for Initial Teacher Education (ITE) courses for the Learning and Skills sector mean that mentors now have a more significant role in the formal assessment of their mentees' practical teaching. This research looks at the emerging dilemmas and challenges and investigates the changing and complex relationship in institutions where both parties are working as colleagues. Data have been collected since 2006 through questionnaires administered during the programme of mentor training, a survey of mentors and mentees and more recently through focus groups, questionnaires and discussions with mentors, as well as semi-structured interviews with a small sample of mentors and their mentees. Data analysis has been informed by a particular model of mentoring by Klasen and Clutterbuck. Besides practical issues and choice of mentor the dilemmas and issues stem from the tensions between the varied roles that mentors play and the boundaries between those roles and those that lie outside these limits. (Contains 4 figures and 4 notes.)