Communication in the mathematics classroom is an element of especial interest in most recent curriculum reform movements. Particular attention is being paid to the nature of classroom interactions and to the negotiation of meanings between teachers and students. The analysis of communication processes and their development in the classroom was the theme of a collaborative project involving three teachers from the same basic school (with students at grades 5-9). Three case studies were made, one of each teacher. These teachers were all very different and very interesting. In this paper, given the space constrains, we choose to present just the case of a teacher, Maria, who experienced the most noticeable change (The reader is referred to Martinho (2007), for a complete account of the whole project and the case studies of the other two teachers). This paper addresses the work of this teacher, discussing her conceptions, practices and reflections on her own practices with respect to classroom communication and how they changed through this collaborative project.