During a six-day U.S. visit in which he called for world peace and met with victims of clergy sexual abuse, perhaps the most difficult task that Pope Benedict XVI set before U.S. Catholics was to raise up a new generation of priests, sisters and brothers.

"Young men and women of America, I urge you: Open your hearts to the Lord's call to follow him in the priesthood and the religious life," he told a cheering crowd in Yankee Stadium.

The need is urgent -- even as the number of Catholics grows, the last large classes of priests ordained in the late 1950s and early 1960s are retiring. Dioceses that ordained 10 or 20 men annually then might ordain two or three today. Ordinations in the United States are up from a low in the 1980s, but since 1997 have hovered between 400 and 600. Few today are attracted to a vocation that requires celibacy.

On the morning after the pope left New York it was clear to Monsignor Edward Burns, the Pittsburgh priest who directs the U.S. bishops' national office for vocations, that the visit had touched Catholics deeply. As he walked down the streets in New York, "people would stop and ask me for a blessing," he said.

"The Holy Father's visit had a great impact. I believe it will help create a vocations culture in which young men will step forward."

Although this 81-year-old pope seems like an unlikely figure to lead a youth movement, many believe he was elected in part to do so. His predecessor, Pope John Paul II, was devoted to reaching young Catholics in ways that some cardinals did not understand or appreciate. But when Pope John Paul died in April 2005 and millions of youth poured into Rome from across the globe to express their love for him, all cardinals realized he had ignited a renewal movement. They elected Cardinal Joseph Ratzinger, his closest collaborator, to continue his work.

Monsignor Burns thought Saturday's youth rally in Yonkers, when 25,000 Catholic young adults responded repeatedly with applause and cheers as the pope called them to bear witness to Christ, would have repercussions far beyond those who were present.

"I'm convinced that the same Holy Spirit that hovered over the disciples with tongues of flame was present at that gathering with the Holy Father," he said.

Among 5,000 seminarians at that rally was Michael Roache, 29, who is slated to be ordained for Pittsburgh in 2011.

"In the pope's talk, he said to just be open to what the Lord is calling you to do, and that will make you happy," he said, adding that is how vocations begin.

"There was a sea of seminarians who were joyful and excited about the Holy Father and life in general," he said. When youth saw them, "I think they realized that this is a joyful thing to do."

Lauren Schlieper, 18, a senior at North Allegheny High School and a member of the St. Alexis youth group in McCandless, was already pondering becoming a sister when she attended the Nationals Park Mass in Washington. While she isn't certain of her calling, "The Mass was an eye-opener, that I should be open to it and not back away," she said.

Being among 47,000 Catholics who were as excited about the faith as she was "made me realize that no matter what your spot in the church is, God has a plan for you," she said. "Even if it's a small job, it's part of something bigger."

The pope modeled that as he encouraged Catholics to look beyond him to Christ, she said. "He seemed like a very humble man. Even though he is the head of the entire Catholic Church, he gave the impression that it is not about him, but about something bigger and better than all of us."

Her fellow youth group member, Michael Reid, had a similar impression. When Pope Benedict celebrated the Eucharist, "you could tell he was really in awe" of Jesus' presence in it, he said.

The pope's most constant theme, whether speaking to bishops, the United Nations or the youth, was the danger of a moral relativism that would allow people to justify any action that felt good to them. Young people understand that message, said Mr. Reid, 18, a senior at North Allegheny High School.

"There are so many forces in the world today that are trying to get you deeper and deeper into sin," he said. "He shed light on that and told us that we should not be sucked into what the world is saying to us."

Gary Slifley, associate director of the diocesan Department for Youth and Young Adult Ministry, led 265 teens and chaperones from the Pittsburgh diocese to see the pope at Nationals Park.

He gave each of them a "Pilgrim Triptych" to jot down reflections about what the pope had said. On the bus ride home, 10 teens on his bus volunteered to speak about their experience.

They "shared a great feeling of unity with the Holy Father and with the church. They felt his warmth and grandfatherly approach really connected, and that his message of hope spoke to them," he said.

"Something like this can transform young people by the planting of seeds," he said. "If they say yes to God today, they will continue to say yes their whole life."

The Rev. Thomas Reese, author of several books on the U.S. bishops and the Vatican, said the pope made no mistakes on this trip, and did seem to bond with youth. But he doubts he will be more effective at inspiring new priests than was Pope John Paul.

"Pope Benedict isn't a miracle worker, though we can always hope and pray," he said.

The pope's cheering fans were sometimes compared to rock fans, and, much like a rock tour, his visit had a title: "Christ our hope." That message of hope will lead to vocations over time, said Bishop David Zubik of Pittsburgh.

"Any time there is a genuine expression and experience of hope, people naturally want to get involved," he said.

The pope walks his talk, he said. "When people see someone who is genuinely happy doing what they are doing, they feel intrigued by what brings them that happiness. An experience like this fires up the engines."