The upper house of Argentina's parliament, the Senate, has voted to abolish amnesty laws which protect members of the former military governments from prosecution for human rights abuses.
Some 30,000 people may have been killed during the Dirty War
The vote opens the way for charges to be brought against hundreds of security officials suspected of murder and torture during the military dictatorship.
The Supreme Court will now have the final say on the matter, but experts say the court - itself undergoing a shake-up after accusations of corruption and political bias - has not signalled whether it will make a ruling.
Human rights group estimate that up to 30,000 Argentines were officially reported as dead or missing during the military dictatorship between 1976 and 1983.
Members of groups representing victims' families lined the hallways of the Senate chamber and shouted "Ole! Ole! Ole!" after the vote.
"Today we are carrying out an act of moral and institutional reparation and reconstruction of Argentina," said
Peronist Senator Cristina Kirchner, the wife of President Nestor Kirchner, just before the vote.
After nearly eight hours of debate, the senators voted 43-7 with one abstention and 21 absent from the vote.
Last week, the lower house of Congress also voted to annul the laws.
The measure now has to be signed into law by President Kirchner, who after his inauguration three months ago launched a series of high-profile initiatives to crack down on impunity.
The courts will then have to sift through the thousands of allegations of torture and murder dating back to the period two decades ago commonly known as the Dirty War.
Experts say the Senate vote is largely symbolic, as the Supreme Court is likely to be the final arbiter on the constitutionality of the laws.
The BBC's Americas editor, Robert Plummer, says it is not yet clear how impartial the court - where some members could face corruption charges - will be as it prepares to rule on the matter.
"No one pressures the court on anything," Carlos Fayt, the head of the court, was quoted by Reuters news agency as saying.
Experts also say that supporters of the laws are expected to appeal to the justice system to maintain them.
In the 1980s, Congress, fearing another military rebellion after decades of coups, passed two amnesty laws.