This paper describes the range of policies that might be used to support fertility rates at a moderate level, that is, around an average of 1.7-1.9 births per woman. The paper argues that in selecting from the range of policy options, consideration must be given to the existing social-institutional framework in the particular country. In other words, there can be no single cross-national model for success. Each country must seek its own institutionally appropriate approach. Also, each country must deal with the realities of its own political economy. Strategies will not be accepted if they are not based upon a social consensus. In addition, as far as possible, policies to support fertility should be based upon a theory or theories as to why fertility has fallen to low levels in a particular setting. Given that fertility-support policies are likely to be expensive in one way or another, some understanding of the nature of low fertility will provide greater efficiency in policy implementation. The paper reviews several possible general theories relating to low fertility. Finally, it is argued that countries should have some notion about what it is that they are aiming to achieve. Inevitably, demographic sustainability (at least zero population growth) is an ultimate aim for all countries. The question is how far into the future is "ultimate"? Or expressed differently, how much of a decline in the size of the population or the labour force is the country willing to sustain before demographic sustainability is achieved? The example of Italy is used to illustrate this point.