Values in mathematics education are those deep, affective qualities which education aims to foster through the school subject of mathematics and are a crucial component of the classroom affective environment. As a result of demands that students become more economically oriented and globally conscious, mathematics educators are being challenged as to which values should be developed through mathematics education. The concern is that, although values teaching and learning inevitably happen in all mathematics classrooms, they appear to be mostly implicit. Thus, it is likely that teachers have only limited understanding of what values are being taught and encouraged. The new questions asked include: (a) What are teachers' understandings of their own intended and implemented values? (b) To what extent can mathematics teachers gain control over their own values teaching? and (c) Is it possible to increase the possibilities for more effective mathematics teaching through values education of teachers and teachers in training? In order to begin to answer these questions, the authors theorize values teaching in mathematics. In this paper the authors analyze three interrelated sources of values which permeate mathematics classrooms: general educational, mathematical, and specifically mathematics educational. The authors also analyze the various influences on teachers' values with regard to explicit and implicit values teaching through an adaptation of Billett's (1998) framework for the genesis of social knowledge. (Contains 64 references.) (Author/ASK)