The fortunes of chance and data have fluctuated in the mathematics curriculum in Australia since their emergence in the National Statement in the early 1990s. Their appearance in Australia followed closely on similar moves in the United States. In both countries the topics, taken together, were given a section status equal to other areas of the mathematics curriculum, such as space or algebra. In Australia this was reflected in the curricula of many states. In recent years chance and data have held their place in the United States, but in some places in Australia have been diluted by being merged with other parts of the curriculum, for example both chance and data with measurement, or chance with number. As discussions proceed on national consistency across the state mathematics curricula in Australia, the place of chance and data appears to be in further jeopardy. In this article, the author explains how the two fundamental ideas of variation and expectation underpin the teaching of chance and data. (Contains 1 figure.)