Substantial, broad and varied benefits can be gained from mentoring; however, the key to successful mentoring lies in the mentor/mentee relationship. The present study investigated the dimensions in the mentoring relationships that foster or impede the mentoring process between four kindergarten principals and four student-teachers in Hong Kong. The findings of the study support the view that relationship-building is critical in the mentoring process. The dimensions that may sustain an effective mentoring relationship appear to be a high comfort level, trust, openness, ongoing support, regular communication, and the mentors' expertise and level of commitment. [Copyright of Early Child Development and Care is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/0300443022000022404]