More than 4,000 Roman Catholic priests in the US have faced sexual abuse allegations in the last 50 years, a new report commissioned by the Church says.
Cardinal Bernard Law was forced to resign at the height of the scandal
The figure represents about 4% of clergymen in the US during that time.
More than 10,000 children - a large majority boys - were allegedly abused, but victims' representatives say this appears to be an underestimate.
A separate report described the church leaders' failure to act effectively as "shameful to the church".
The head of the US Conference of Catholic Bishops, Wilton Gregory, repeated the church's apology to all those who had suffered abuse from members of the clergy and appealed for victims to come forward.
But, in a BBC interview, a spokeswoman of the survivors of church abuse accused the Church of continuing to protect the perpetrators and urged the bishops to release their names to the public so a database could be established.
The National Review Board - a lay watchdog panel formed by the bishops - issued two studies documenting the molestation problem from 1950 to 2002.
The first report details the scope of the "epidemic of child abuse" - 10,667 claims.
More than 80% of the alleged victims were male and over half said they were between the age of 11 and 14 when they were assaulted - with alcohol and drugs the single most usual enticement.
Abuse by clergy increased suddenly in the 1950s and 1960s and peaked in 1970 - one in 10 priests ordained in that year was accused of abuse.
ABUSE FIGURES 1950-2002
10,667 children victimised by 4,392 priests
More than 80% male 11-14 years old
4% of US Catholic priests involved
More than 10% of claims could not be substantiated
About 20% not investigated because accused priest was dead or inactive when allegation received
40% of the abuse took place in rectories
97% of 195 dioceses, plus 142 religious communities filled out surveys
The second report examined the causes - based on interviews with clergy, victims, and experts on sex offenders.
It blames US bishops for their failure to screen applicants to seminaries and for recycling abusive priests between parishes rather than dismissing them.
"These leadership failings have been shameful to the church," the report said.
"Many dysfunctional and psychosexually immature men were admitted into seminaries and later ordained in the priesthood," said Robert Bennett of the National Review Board.
More to come?
Some Roman Catholics will hope the report will help to close a painful and humiliating chapter in the Church's history, says the BBC's religious affairs correspondent Robert Piggott.
But Barbara Blaine, president of SNAP - a network of survivors of abuse - dismissed the figures, which had been provided in "a voluntary self-survey" by the "same bishops who had shielded the perpetrators".
Victims' groups say the figures are much higher
Bishops refused to disclose the names of perpetrators, instead of just numbers "which are useless", Ms Blaine told the BBC's Newshour programme.
She said that only 5-10% of victims of child sexual abuse reported the crime - far fewer did in the case of abuse by priests.