The article examines negotiations for the 1995 Mekong Agreement, signed by Cambodia, Laos, Thailand, and Vietnam. A ``negotiation analysis'' approach is used, which is based on understanding interests and ``no agreement'' alternatives. The article draws upon interviews by the author with approximately 25 principals in the negotiations. Thailand and Vietnam, the regional powers, wanted to build cordial relations in the aftermath of the Cold War, and needed the Agreement to help contain conflict and promote cooperation on water resources. Laos and Cambodia were motivated to reach an accord to help procure aid. Planned Chinese hydropower reservoirs may increase the dry season flow – allowing the lower Mekong countries to share future increments of dry season flow. Negotiation assistance by UNDP was necessary to overcome a legacy of mistrust. Key articles of the Agreement deal with maintaining dry season flows, notification procedures, and a Basin Development Plan.