Relatives of people abducted, murdered and secretly buried by the Provisional IRA and other republican groups will march on Stormont today in a bid to get the bodies back.
Families of nine people known as Northern Ireland's disappeared will carry a black wreath and nine white lillies in an All Souls' Day ceremony commemorating their loved ones.
In October 2003, the Provisional IRA apologised for the grief suffered by the families of the disappeared in Northern Ireland.
However, despite receiving information from the Provisionals, the Commission for the Recovery of Victims' Remains has located only some of the bodies.
The victims include 17-year-old Columba McVeigh from Dungannon, Co Tyrone, who vanished in 1975 after republicans accused him of being an informer.
The last search for Mr McVeigh was carried out in 2003 by Garda excavation teams on bogland at Bragan Mountain close to the Tyrone-Monaghan border.
Fresh tests were carried out in Co Monaghan last week.
They also include Kevin McKee, from west Belfast, who disappeared along with Seamus Wright, 25, in 1972; Brendan Megraw, 23, kidnapped in 1978 from west Belfast; Danny McIlhone, who disappeared from Dublin in 1981; Seamus Ruddy, 33, who went missing in Paris in 1985 after a dispute with the Irish National Liberation Army.
While the Provisionals are believed to have murdered 29-year-old undercover soldier Robert Nairac who was last seen in a south Armagh pub in 1977, republicans have also been blamed for the disappearance of Gerard Evans, 24, who vanished on his way home to Crossmaglen in south Armagh in 1979 and Charlie Armstrong, 55, who vanished in the same town in 1981.
However the IRA has not claimed responsibility for the disappearance of Mr Armstrong and Mr Evans and virtually no information has been forthcoming about Captain Nairac's burial site.
Sinn Féin leader Gerry Adams has nevertheless appealed for information about the whereabouts of Mr Armstrong and Mr Evans' remains.
As the families prepared to march today, North Belfast priest Fr Aidan Troy said: "What we are doing on All Souls Day is in memory of their loved ones and it is also a reminder of the obligation on all of us to do what we can to bring closure for the families."
Members of a cross-community organisation which represents the bereaved, Wave, will also be present.
"The feeling of loss is different for every family and we respect this, however it is particularly difficult for the families of the disappeared as they have no grave to mark their loved ones' resting place," chief executive Sandra Peake said.