When the Soviet Union collapsed in 1991, Ukraine had the world’s third largest nuclear arsenal on its territory. When Ukrainian-Russian negotiations on removing these weapons from Ukraine appeared to break down in September 1993, the U.S. government engaged in a trilateral process with Ukraine and Russia. The result was the Trilateral Statement, signed in January 1994, under which Ukraine agreed to transfer the nuclear warheads to Russia for elimination. In return, Ukraine received security assurances from the United States, Russia and Britain; compensation for the economic value of the highly-enriched uranium in the warheads (which could be blended down and converted into fuel for nuclear reactors); and assistance from the United States in dismantling the missiles, missile silos, bombers and nuclear infrastructure on its territory. Steven Pifer recounts the history of this unique negotiation and describes the key lessons learned.