Upon the breakup of the Soviet Union, Ukraine inherited the third largest nuclear weapons stockpile in the world after the Russian Federation and the United States. However, in the January 1994 Trilateral Statement, Ukraine committed to full disarmament. Kiev joined the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as a non-nuclear weapon state in 1994, acceded to the Strategic Arms Reduction Treaty (START I), and having transferred all of its nuclear warheads to Russia for elimination, became nuclear-weapon-free in 1996.
http://www.nti.org/country-profiles/ukraine/nuclear/
>> having transferred all of its nuclear warheads to Russia for elimination, became nuclear-weapon-free in 1996.
Bet they wish they had a do-over on that one.