Despite the availability of hardware and software, the mathematics staff in a technology-rich secondary school rarely used computers in their teaching. This study investigates the reasons for this phenomenon. The results indicate that individual teachers’ resistance was related to their beliefs about mathematics teaching and learning and their existing pedagogies, including their perceptions about examinations, concerns about time constraints, and preference for particular text resources. It was also found that teachers with transmission/absorption images of teaching and learning and teacher-cent-red, content-focused pedagogy had a restricted image of the potential of computers in mathematics teaching and learning. By contrast, one teacher with images of teaching consistent with social constructivist learning theory and a learner-focused pedagogy had a broader image of the potential of computers in mathematics teaching. Further, staff discourse was also found to be important in determining whether computers would be used by students to facilitate their conceptualisation of mathematics. These finings have implications for professional development related to the integrated use of computers in mathematics teaching.