Teacher unions are increasingly perceived as principal stakeholders in determining the overall effectiveness of school systems. This paper presents findings of a study that explored how teacher union leaders construct meaning about teachers' self-interests and education interests. Data were collected through interviews with 18 teacher union leaders in a teacher organization in an eastern Canadian province. Respondents overwhelmingly agreed that the teacher union had dual roles--to promote both the economic welfare and professional development of teachers. Less frequently mentioned (65 percent of participants) was a third role, that of promoting quality education. Only 12 percent mentioned a fourth role of the union, a concern for social justice. Factors that influenced the construction of the union's role included membership issues, the government's policy agenda, the degree of public support for union goals, and the extent to which members shared a local or provincial perspective. The study found that the self-interests and the educational interests of teachers are interdependent, complementary opposites. In times of crisis union members concentrate on their immediate needs and sometimes lose sight of the larger picture. However, teachers eventually realize that their immediate needs cannot be met without attending to the long-term best interests of the educational system. Economic welfare and professional development are complementary forces that may be pulled to a higher level by a mutual concern for quality education and social justice. Understanding this relationship can serve as a bridge to developing productive relationships between union and management, and between union and government that may lead to renewal and growth for the education system. (Contains 27 references.) (LMI)