On 11 December 2008 the UN General Assembly adopted a set of draft articles on the law of transboundary aquifers which had been prepared by the International Law Commission (ILC) between 2002 and August 2008. These draft articles are the first official instrument that lays down rules of international law for the management and protection of groundwater, which makes up 97 per cent of the Earth's freshwater resources, excluding the resources locked in polar ice. This article discusses the contribution of the draft articles to the development of international water law. It first provides some background on the importance of shared groundwater resources, then describes the ILC's work on transboundary aquifers, and finally assesses in detail the draft articles and the way ahead.