This is the fifth in a series that examines the challenges that teachers in different domains face as they attempt to implement the pedagogical reform "Fostering a Community of Learners" (FCL). Here we focus on the relationship between FCL and the teaching of mathematics. We argue that it is possible to teach mathematics through the FCL pedagogy, but that doing so requires some rethinking of both mathematics instruction and FCL. In particular, we describe three shifts that aided a teacher's implementation of FCL pedagogy with mathematics: the teacher developed a new perspective on mathematics that emphasized the importance of having students learn both mathematical concepts and processes; the teacher developed a new understanding of the role of the teacher in mathematics-education reform; and the teacher modified his understanding of FCL, coming to believe that a discourse community could be the basis for FCL pedagogy in a mathematics classroom.