The US Supreme Court will hear arguments on March 26 and 27 on the sensitive topic of gay marriage, one of the thorniest social disputes in modern America.
Same-sex marriage is currently barred by a federal law, yet legal in nine states and the capital, Washington.
The court's announcement last month that it would take up the issue received cheers from opponents and advocates of the practice alike, who said a ruling by the justices could help settle the topic.
In announcing its schedule Monday, the court said it would take up the question of California's ban on same-sex unions first, on March 26, and then the next day hear challenges to a federal law denying benefits to same-sex couples.
The court is expected to hand down its ruling in June.
The country's highest court set aside an hour for each case, but observers believe that the hearings could well last much longer, because President Barack Obama's administration as well as a group of elected Republicans have each been called to give their opinions.
On March 26, the Supreme Court will consider whether the 14th amendment to the US Constitution, which requires states to provide equal protection under the law to all people, would bar California from defining marriage in its own constitution as "between one man and one woman."
If the court decides against the California ban, its decision could affect the 31 other states that forbid gay marriage in their constitutions or legislation.
Then on March 27, the court will turn to the federal Defense of Marriage Act, or "DOMA," which defines marriage as the legal union of one man and one woman and denies federal benefits to married same-sex couples.
These benefits include inheritance rights, tax breaks, filing of joint income tax returns, and health insurance coverage.
Obama's government does not support this view of marriage and would like the law to be overturned, but conservative campaigners are urging the Supreme Court to rule that the act is constitutional.
The court will focus on the case of Edith Windsor, a gay woman legally married in Canada who has been told to pay tax on inheriting the estate of her deceased partner.
The Supreme Court will rule whether DOMA violates the guarantee of equal protection under the law as guaranteed by the fifth amendment of the US constitution.
It will also decide if the Obama administration's position that DOMA is unconstitutional deprives the Supreme Court of jurisdiction, and whether a complaint by some US lawmakers has legal standing.
There are 50,000 to 80,000 same-sex couples who have been married legally in the US.
Correction: This headline originally referred to Prop 9.