A review of projection methodologies used to project sub-acute inpatient activity in various international health care jurisdictions was undertaken as part of a project to develop subacute inpatient activity projections for the state with the largest population in Australia. The literature search identified nearly 200 articles and found three main groups of projection methodologies: projections with a focus on subacute care; projections with a focus on acute care, but which often included subacute activity in the overall projections; and projections of specific diseases/conditions influencing the demand for subacute care. In terms of the examples in the literature specifically regarding subacute care, the most common method of estimating current or future need was the use of normative benchmark ratios of beds to population. This was mainly to provide a policy basis to encourage development of subacute services, but also because of convenience. In the literature regarding acute activity projection methodologies, many incorporated subacute activity in the overall activity measures of the acute hospital unit. The most common method of acute care activity projection was use of current or trended utilisation rates applied to population projections. It appears that a significant amount of planning and demand projection being undertaken internationally on subacute care takes place within acute care methodologies. In regard to the potential use of specific diseases/conditions that drive demand for subacute care, such as stroke or cancer, it is suggested that the best use of these disease-specific projections is in reality testing the results of other modelling. A number of conclusions are made and issues highlighted regarding projections of subacute inpatient activity.