This paper explores the interrelationship between performance teachers' professional identity and the various forms of professional knowledge they bring to their work. The data derive from an ethnographic case study conducted across a period of 12 weeks in each of two distinct music training institutions in Greece--a University Music Department and a Conservatoire. A total of 28 teachers participated in the study across institutions (Conservatoire, n = 18; Music Department, n = 10) and within each institutional sample four teachers were observed during their teaching and performing practices. Institutional documents provided contextual information. Findings showed that performance teachers drew on different forms of professional knowledge in their teaching practice in accordance with the construction of the more valued identity in their workplace as either a teacher or a performer. Also evident was that a particular identity and forms of professional knowledge were foregrounded at the point where teacher and performer identities met or separated. The development of a new type of professionalism at the interface where performer and teacher identities meet thereby empowering teachers to take on roles and responsibilities that would extend their professional stories of self is discussed. (Contains 2 figures and 5 notes.)