This chapter reviews the literature on aspects of early number learning for children with Down syndrome. It reports on data relating to early number from a larger study undertaken to map the mathematical development of children with Down syndrome. The study used semi-structured, task-based, one-to-one interviews. From the analysis of video data, it would appear that the children in our study are developing counting in different ways from typically developing children. It seems that the development of number understanding by these children is enhanced by the use of symbols, but more research is needed. Suggested teaching approaches are proposed, as are further areas for research.