The families of those killed and injured on Bloody Sunday and the soldiers involved are studying Lord Saville's report on the events.
The outcome of the Bloody Sunday inquiry, the longest and most expensive public inquiry in UK legal history, is due to be made public later.
Thirteen people died in 1972 when British soldiers opened fire on civil rights marchers in Londonderry.
The Saville Report was made available to the families' legal teams earlier.
The report was delivered to the Guildhall in Derry at 0200 BST on Tuesday. It cost £195m and took 12 years to complete.
The shootings were among the most controversial state killings in the Northern Ireland conflict.
The marchers were shot dead on 30 January 1972 when British paratroopers opened fire on crowds at a civil rights demonstration. Fourteen others were wounded, one of whom later died.
More than 25 years later, in 1998, then Prime Minister Tony Blair established a full inquiry under the auspices of former High Court judge, Lord Saville of Newdigate.
Friends, relatives, politicians and well-wishers accompanied the families of those killed to the city's Guildhall.
As each of them went into the building, they raised aloft a placard bearing the picture of their dead relative, as the assembled crowd clapped and cheered.
Kay Duddy, whose brother Jackie was the first person to be shot on Bloody Sunday, will be among the first of the family members to see the report.
"We've waited so long for this, and now we're finally here, my stomach is in knots," she said, before going into the Guildhall to read it.
"So many times we thought we were so close, and to think that soon we'll see it in black in white... I just hope I can get throught the day," she said.
In her handbag, she carried a handkerchief marked 'Fr Edward Daly' - the same white handkerchief that the priest used to try and staunch the blood from her dying brother's wounds.
She said she carried it to give her strength on this important day.
The families will not come out again until at least 1530 BST, when the contents of the report they are now reading will be revealed to the world.
