Studies such as the Effective Teachers of Numeracy Study (Askew, Brown, Rhodes, Johnson, & Wiliam (1997) have contributed much to our understanding of what constitutes effective teaching of numeracy. This paper aims to build on these findings and to contribute a model that could be used to understand teachers' numeracy practices and the factors that influence these practices. Through a synthesis of the literature, the author has devised a set of principles of practice which encapsulates effective teaching of numeracy and has identified six teacher actions which can be used to enact these principles. Findings from case studies conducted with three teachers indicated that the model provided a useful framework for observing and understanding classroom numeracy practices. (Contains 2 footnotes, 1 table, and 1 figure.)