Pope Benedict XVI has opened two days of talks with Ireland's Roman Catholic bishops to discuss their response to a child sex abuse scandal.
In a report issued last year the Church admitted covering up abuse for decades.
At a Mass in Rome before the meeting one of the Vatican's top cardinals called the abuse "abominable".
Four bishops criticised for failing to address concerns about abuse have already resigned. But victims say more must be done to restore public trust.
Last year, a report was highly critical of the Dublin Archdiocese's handling of priests who were suspected sex abusers.
The Murphy Commission laid bare a culture of concealment where Church leaders prioritised the protection of their own institution above that of vulnerable children in their care, and often failed to pass on details to the police.
The Pope has said he is "disturbed and distressed" by the report and shares the "outrage, betrayal and shame" felt by Irish people.
'Enormous injustice'
Before the meeting began on Monday, the Vatican Secretary of State Tarcisio Bertone held a Mass attended by the Irish bishops.
He called the sexual acts committed against children "particularly abominable".
He said the scandal was "humiliating" but that the Church must face the challenge.
"Every kind of challenge can become a reason for purification and sanctification as long as it is illuminated by faith," he said.
Armagh Archbishop Sean Brady, the primate of all Ireland, told Vatican Radio that the two days of meetings were part of a "journey of repentance, reconciliation and renewal".
BBC religious affairs correspondent Christopher Landau says bishops from a particular country normally visit the Vatican around once every five years.
But the Pope has summoned Ireland's bishops for a special two-day meeting, specifically to address the issue that has severely undermined Catholicism's standing there, our correspondent says.
The Report of the Commission of Investigation into the Catholic Archdiocese of Dublin - the Murphy report - published in November, found the Church had "obsessively" hidden child abuse from 1975 to 2004, and operated a policy of "don't ask, don't tell".
Some bishops still in office had been part of the cover-up, the report said.
Four out of five key bishops who were particularly criticised have now resigned, but the fifth, Bishop of Galway Martin Drennan, is expected to meet the Pope.
Groups of abuse victims have written an open letter to the Pope, calling on him to demand the resignation of Bishop Drennan, who has insisted he did nothing to endanger children.
They are also asking the Pope to instruct the bishops "to comply fully with civil child protection guidelines, including the mandatory reporting of all concerns or complaints to the civil authorities for investigation".
'Truth must out'
On Sunday, one of the prelates said they would acknowledge the "failure on the part of all of us" to be vigilant against abuse and express their commitment to try to rectify "the enormous injustice and cruelty" the victims suffered.
"A casualty of all this has been the truth," the Bishop of Clogher, Joseph Duffy, told reporters at the Irish seminary in Rome. "The fullness of the truth must come out, everything must be laid on the table."
Bishop Duffy said questions of resignation would not be "on the agenda of the bishops because that is not our prerogative".
Our correspondent says Ireland's bishops know that much has to change if the Church is going to regain even a fraction of the standing it had in national life a century ago.
But as elsewhere in Europe, dwindling congregations and a shortage of priests make for furtheruncertainty about the Church's future, he adds.
