The ageing of the Australian population and its implications are now well-established on the Australian public policy agenda. Part of this interest is in its impacts on the Australian workforce. It is less well known that different segments of that workforce have quite different age structures. The academic sector has one of the oldest workforces of all groups and this paper analyses its contemporary age structure and its evolution. It shows how uneven growth of universities over the last 40 years and changing human resource practices have contributed to university staff being heavily concentrated in the older age groups. It also shows how international migration of academics to and from Australia is influencing the academic age structure. A case study of the staff of one Australian university is used to show the impact of ageing on future staffing and indicates that Australian universities face a massive recruitment task over the next decade due to the retirement of the large numbers of academics who began work in the 1960s and 1970s. Some of the implications of this for universities are then explained.