The sustainable management of international rivers was affirmed as a policy priority in Agenda 21 and figures as a key mandate of the Global Environment Facility. Yet, the institutions needed to translate such sustainability goals into reality are in most regions sorely lacking. As home to one of the first international river management institutions in the developing world, the Mekong River Basin offers a host of lessons on the_challenges of building effective transboundary governance. The adoption of explicit sustainability goals by the Mekong River Commission, as described in this chapter, has created a mandate for environmental protection and social welfare, but in practice the incentives for regional economic development are often at odds with the interests of communities who depend directly on the basin's resources for their livelihoods. Growing regional economic ties are providing a new rationale for cooperation, but strengthening transboundary governance of the river system in support of sustainable livelihoods will require increased engagement by civil society actors as well as governments and multilateral agencies from outside the Mekong region.