Families of those who were killed in the Dublin-Monaghan bombings say they need truth and justice.
Taoiseach Micheal Martin will be among those attending a commemoration in Dublin city this morning marking 48 years since the atrocity.
33 people, including a pregnant woman, were killed in four blasts in Dublin and Monaghan - 300 others were also injured.
A 2003 report into the 1974 bombings by Justice Henry Barron criticised An Garda Siochana at the time for prematurely closing its investigation.
Margaret Urwin from Justice for the Forgotten, says the Dublin-Monaghan bombings saw the highest death toll of The Troubles.
"No day saw a greater loss of life than the 17th of May 1974," she added.
"For many years there were no commemorations; there was nothing, not even a memorial built to the victims.
"Thankfully that situation has been remedied and the families are able to gather together."
