President Nursultan Nazarbaev signed a decree today changing the city's name to Semey.
Nazarbaev said earler this month the name "Semipalatinsk" carried negative associations that put off foreign investors.
The Semipalatinsk district was used as a Soviet nuclear test ground between 1949 and 1989.
(RFE/RL's Kazakh Service, Interfax-Kazakhstan)