 On March 11, 1990, he signed the Act of the Re-Establishment of the State of Lithuania, declaring Lithuania's independence from the Soviet Union.In January 1991, when the first government led by Kazimira Prunskienė resigned due to rising prices, Šimėnas became the Prime Minister of a largely unchanged government.However, as the Soviet Army entered Vilnius and surrounded key buildings, Šimėnas disappeared.