Taoiseach Enda Kenny has said it is time for anyone with information about what happened to any of "The Disappeared" to come forward.
He said people with information should engage with the commission set up by the last government so that closure can be brought to the victims' families.
Mr Kenny said it appears that those who are still disappeared are in counties Meath or Monaghan.
He said the events happened a long time ago, but said the hurt is still palpable.
Last night's documentary on RTÉ, The Disappeared, looked at those killed and then secretly buried by the IRA.
Mr Kenny was responding to statements in the Dáil by Sinn Féin leader Gerry Adams.
Mr Adams said he had worked closely with the commission and that the programme should be a huge motivation to anyone who has any information whatsoever to bring it forward.
Fianna Fáil leader Micheál Martin said far more needs to be done to seek information for the victims' families.
He asked that every effort is made to pursue the murderers of Jean McConville.
Ms McConville, a mother-of-ten, was taken from her west Belfast home in December 1972 on suspicion of being a British informant.
It is believed that she was tortured before being shot and buried.
Mr Martin also referred to the Programme For Government, where victims' rights legislation is promised.