This paper estimates and discusses some of the potential labour market implications arising from the rapid ageing of government employees in a number of OECD countries. Under alternative scenarios for future public employment policies, available labour resources for the private sector are estimated taking into account the declining age cohorts entering the labour market. These scenarios suggest that, in the absence of considerable increases in labour utilisation, maintaining government sector hiring at their historical share of new labour market entrants will entail sharp declines in the production of government services. On the other hand, if present levels of government services are to be preserved, governments are likely to hire an increasing share of labour market entrants, creating a strong crowding-out effect for the private sector. Alternatively, productivity in the government sector would have to increase substantially.