During the Cold War the United States detonated sixty-seven nuclear weapons over the atolls of Bikini and Enewetak in the Marshall Islands. In the late 1970s the United States addressed the massive amount of residual contamination by abandoning Bikini as permanently uninhabitable and pushing much of the waste at Enewetak into the open lagoon. Much of the plutonium was dumped into the crater that had been left by an atomic bomb explosion, and then covered with a thin shell of cement. The resultant “Runit dome” sits unmarked and unguarded in a small island and one day will be submerged by the rising waters of the Pacific Ocean, unless it is first torn apart by typhoons. Radiation from the Marshall Islands has already been detected in the South China Sea. Using the experience of the Marshall Islands as a case study, this article seeks to shed light on the environmental and security challenges of nuclear waste disposal in the Pacific and beyond.