Fiona McDiarmid and Ruth PritchardNumeracy has been a major focus of recent professional development initiatives for primary school teachers in many countries. Research has shown that a variety of factors contribute to a school?s ability to sustain gains after completion of professional development programmes. An exploratory action research study undertaken with five inner-city primary schools focused on identifying and providing a variety of tools to sustain effective numeracy practices. Teacher surveys, professional discussions with staff, and classroom observations informed the intervention. Numeracy facilitators/researchers worked with principals and Lead Teachers in mathematics to develop increased knowledge and understanding of issues surrounding numeracy teaching and learning. A central theme was the use of reflective practices which promoted the use of critical peers, observation, and videoing of mathematics lessons. Major issues found to be inhibiting sustainability included: leadership and staff changes within schools, a lack of school wide numeracy policies, and teachers? lack of in-depth knowledge of numeracy content and pedagogy. Interim findings suggest that teachers require further support and opportunities to experiment with, and reflect on, new ideas encountered within the professional development. Offering external support, creating a forum to address the issues, and promoting professional learning communities within the schools, enabled the schools to refocus on effective numeracy practices. Some reluctance by teachers to deprivatise or critically reflect on their practice was apparent. Round table participants are invited to contribute to a discussion of factors which may contribute to the sustainability of effective numeracy practices, to inform further research.