This paper explores the role of oral language and representations in negotiating mathematical understanding. The data were gathered from two Indigenous Australian classrooms in Northern Queensland. The first classroom, a Year 6/7 consisted of 15 students whose ages range from 10 years to 12 years with eight being Aboriginal, six from Torres Strait and one from Papua New Guinea. The second classroom, a Years 4/5/6 classroom consisted of 14 Year 3/4/5 students, with eight being Aboriginal and six of Torres Strait Island origin. Both teachers had been working in this context for up to five years and were perceived by both the school community and local educational consultants as exemplary teachers of Indigenous Australian students. Data were gathered from conversations with the two teachers, and from videos of their lessons especially designed to illuminate issues they negotiate on a day-to-day basis when teaching mathematics. The results indicate that explicit consideration needs to be given to the careful development of precise mathematical language and concrete mathematical materials, the use of questioning in establishing classroom discourse, and the recognition that many of these classrooms are bilingual. (Contains 2 figures.)