The concept of replacement migration was developed by the United Nation Population Division and introduced in 2000. The principal idea of this concept is based on a quite simple approach: How much net-immigration is necessary to reach certain goals concerning the size and structure of the future population? For example: How much net-immigration is needed to keep the population size constant or to stabilise the relation between the labour force and the retired people (dependency ratio)? For the first time the concept of replacement migration is applied to Austria, and concrete projections are presented in this article. The projections clearly demonstrate the need for further net-immigration, but also emphasise the necessity to introduce different political measures to keep the labour market functioning and to stabilise the age-related welfare system. If demographic change ought to be compensated only by migration, the sheer size of future migration flows would exceed any reasonable limit.