Public trust funds can serve useful functions, particularly in resource or aid-dependent economies like those of the South Pacific islands. They serve to enhance savings, and to stabilise and sterilise large natural resource revenue flows. But these funds are susceptible to political forces that undermine their effectiveness. Mechanisms to check these influences, such as statutory independence, broadly based board membership and public reporting, should be in place. Decision rules on drawdowns from the funds need to be carefully selected to avoid disrupting fiscal management.