Global philanthropy is remaking the relationship between the world's rich and poor. Private aid - aid provided by foundations, corporations, non-governmental organisations, and individuals - has doubled over the past decade and may soon overtake 'official' foreign aid. Something of a consensus has developed around the emergence of private aid - that is it is less prone to corruption and more likely to benefit the poor. While private aid has the potential to be a more effective form of aid, it remains vulnerable to many of the same problems affecting official development assistance. Private aid that is both accountable and well monitored, however, can potentially catalyse more competitive markets for foreign aid, and dismantle the monopoly held by traditional bilateral and multilateral donors.