BOB ABERNETHY, anchor: Several reports this week predict Pope Benedict XVI will approve a document being prepared that would bar all homosexuals from becoming Catholic priests -- this just before Vatican representatives begin long-planned visits, inspections, at every American Catholic seminary where, among other things, the visitors are expected to review each school's policy for screening out applicants who are gay or have even a homosexual orientation. There are about 4,500 seminarians.

Judy Valente has our story.

JUDY VALENTE: These candidates for the priesthood have just arrived at Mount St. Mary's Seminary in Maryland. The seminary is nearly 200 years old and one of the largest in the country. Like other seminaries and schools of theology, it will soon be visited for several days by one of the teams of American bishops and priests selected by the Vatican.

Monsignor STEVEN ROHLFS (Rector, Mount St. Mary's Seminary, Maryland): They've been asked to interview all of the seminarians. Every single one. They've been asked to interview all of our faculty, all of the administration. We had to provide all the course work that we teach -- all the outlines, all the bibliographies. They'll interview all of the professors.

VALENTE: The teams will also look for "evidence of homosexuality." Archbishop Edwin O'Brien is coordinator of the seminary review.

Archbishop EDWIN O'BRIEN: We don't want our people to think, as our culture is now saying, that there's really no difference whether one is gay or straight, is homosexual or heterosexual. We think for our vocation that there is a difference, and our people expect to have a male priesthood that is -- sets a strong role model of maleness.

VALENTE: Father Robert Silva is president of a national organization of priests.

(To Rev. Silva): How can anyone determine with certainty that a man is a homosexual?

Reverend ROBERT SILVA (President, National Federation of Priests' Councils): You can't. Going in and saying, "This man is homosexual" -- I just think that that's impossible to do.

VALENTE (To Rev. Silva): Given the current state of research?

Rev. SILVA: Exactly.

VALENTE: In the past, many seminaries focused on the intellectual and theological training of priests rather than their personal development. Experts say that as a result, some priests left the seminary ill equipped to live out the celibate ministry required of them.

That led to problems, including the sex abuse scandal. The Church has not linked child sex abusers with homosexuality, but the scandal did raise questions about the number of homosexuals in the priesthood and in seminaries.

PATRICIA KELLY (Psychologist): The Church, fortunately, has had this huge wake-up call that has put it in a place where it says: "Whoa, we got to ask the right questions, and we can't be afraid of the answers." And that's very much happening.

VALENTE: Patricia Kelly, in consultation with dioceses, does psychological assessments of young men who are candidates for admission to seminary. She says there is now more discussion of sexuality in the context of living a celibate life.

Dr. KELLY: We're looking at the whole person, and sexuality is a big part of it. We are really looking at how this person not only has respect for himself, but has respect for other people and understands his sexuality.

VALENTE: The assessments include FBI background checks as well as questions about spending habits and past relationships. And yet ...

Msgr. ROHLFS: Psychology is a very inexact science. They can raise flags, but they can't tell you for certain that someone is like this. They can just alert you to the possibility that there's a problem here.

VALENTE: The Church calls homosexuality "intrinsically disordered" and actually, since the 1960s it has had a policy that homosexual men not be ordained. But in the 1970s, says Archbishop O'Brien, shifting moral standards and the rush of men leaving the priesthood led some seminaries to ignore that policy. And a few years ago, a leading seminary rector even wrote of the "growing perception ... that the priesthood is, or is becoming, a gay profession."