Today, in the prayer dedicated to ''confession of sins against the people of Israel,'' John Paul did not mention the church's behavior during the Holocaust, just as he did not elaborate on other sins of the church. He said, ''We are deeply saddened by the behavior of those who in the course of history have caused these children of yours to suffer, and asking your forgiveness we commit ourselves to genuine brotherhood with the people of the Covenant.''

Rabbi Marvin Hier, dean of the Simon Wiesenthal Center, called today's apology a ''bold and important step forward,'' but added that he was disappointed that the pope had not mentioned the Holocaust explicitly. ''The church still wants to steer clear of dealing with the role of the Vatican during World War II,'' he said.

The pope also acknowledged that church followers had ''violated the rights of ethnic groups and peoples and shown contempt for their cultures and religious traditions.'' He deplored divisions between Catholicism and other branches of Christianity, and also discrimination against women. ''Given the number of sins committed in the course of 20 centuries,'' Bishop Piero Marini, who is in charge of papal ceremonies, said before the Mass, ''it must necessarily be rather summary.''

The need for Catholics to examine their collective conscience is something that this pope has been thinking about for years, and he laid out his rationale for it in a 1994 apostolic letter called ''The Coming of the Third Millennium.'' He also raised the subject privately in meetings with key cardinals, and his proposal was sufficiently ground-breaking that they requested that the theological and historical implications first be studied in depth.

The result was a dense 31-page treatise by the International Theological Commission, which, with Vatican oversight, ground out the theological precedents and also the limits to the apology.

Written by a committee and released earlier this month, the document addresses concerns that the apology will be misunderstood or misused by those ''hostile to the church.'' It also reflects other worries of theologians, who had to grapple with such complex issues as how a church that considers itself holy can admit mistakes, and whether it is fair for today's church to condemn acts by previous generations made in good if misguided faith.

The document explains that the church is holy, but is stained by the sins of its children, and requires ''constant purification.'' It implies but does not directly address the delicate issue of whether past church leaders also erred.