The planning of long-term care in the community as an alternative to in-patient care requires accurate information on the likely expense of altering the balance of provision. Unfortunately, as very few long-stay psychiatric hospitals have yet closed, the planning of these resource requirements has had to proceed in a vacuum. By examining the costs of community reprovision for the first 136 people to leave Claybury and Friern Hospitals, a prediction equation has been estimated from existing data which links the hospital-assessed characteristics (including psychiatric symptoms and behavioural problems) of these people to the subsequent cost of community care. About a third of the observed variation in these costs can be explained statistically by these ‘baseline’ characteristics. However, the first cohorts exhibit fewer behavioural problems and other symptoms of mental illness, they have been in hospital for shorter lengths of time, and they are younger. The prediction equation for the leavers is thus used to extrapolate community costs for those hospital residents yet to leave. It is found that community costs are lower than hospital costs, not just for the first cohorts of leavers, but for the full populations of the two hospitals scheduled to close.