SAO PAULO, Brazil - Straitlaced clerics deride the new "happy clappy" Catholicism, and here, in a converted bottling plant in the city's shabby market district, Sunday morning Mass really is a laughing matter.

Loud guffaws and applause from 10,000 worshipers heat the air in the cinder-block Church of the Byzantine Rosary. On stage, the Rev. Marcelo Rossi - former exercise instructor, now celebrity priest - delivers a sermon that trips lightly through jokes and shtick, carried to the far corners by 15 speaker towers.

Soon, the vast room is a sea of swaying arms stretched toward naked fluorescent lights on high. Rossi is leading his followers in a bit of antic choreography that he calls "Aerobics for the Lord." As they spin, the corrugated ceiling begins to hiss. Ghostly clouds of water vapor float down to cool the crowd.

In the last quarter of the 20th century, the Roman Catholic Church hemorrhaged Brazilian members by the millions, giving rise to predictions of an unstoppable slide into the ranks of minority faiths in this, its largest bailiwick on Earth.

Yet Rossi's charismatic brand of Catholic worship has defied the prognosticators. For an outdoor Mass during Holy Week, he can pull a crowd of more than a half-million people. Even on workaday evenings, thousands flock to Byzantine Rosary to laugh, sob, shake, and speak in the fevered babble of tongues.

Rather than Rome's lockstep liturgy, his ecstatic services are more like those of the highly nimble competition, Protestant Pentecostalism. If Catholicism is to hold its ground in Latin America, it may have to increasingly look and sound like this.

"Padre Marcelo brought me back," said one of his young followers, Veronica Maria Pereira de Lima, 28, a salesclerk who had drifted from the church. "He's the modern-day priest. The others are stuck in the past. If they carry on with the old style - droning on, standing, kneeling, standing - people will keep leaving."

She added, "I think other priests are finally realizing they have to pay attention to him."

Marketplace of faiths

On the summit of Rio de Janeiro's Corcovado Mountain 250 miles to the east, the statue of Cristo Redentor, Christ the Redeemer, stands as a symbol of Catholic dominion over this land since the 16th century. It is also a reminder of what has been lost, unlikely ever to be regained.

An estimated 450 million Catholics - almost half of the church's global population - live in Central and South America, Mexico and the Caribbean. But in at least a dozen countries, including Chile, Honduras, Argentina and Peru, memberships have dropped anywhere from 10 to 25 percent in a little more than three decades.

In Brazil's 1970 census, 92 percent of its people identified themselves as Catholic. In 1990, 84 percent did. In 2000, when 170 million citizens were counted, 74 percent said they were Catholic. Of those, according to the church, just 10 percent attended Sunday Mass.

The disaffected have helped fill a new and aggressive marketplace of faiths, ranging from Protestant Pentecostalism to Buddhism, New Age mysticism, and African animism.

"We can no longer say Latin America has a Catholic soul," said Bishop Pedro Luiz Stringhini of the Sao Paulo Archdiocese.

The most dramatic losses occurred in the span of three pontificates, the longest being that of John Paul II. His many visits over 27 years, conservative appointments to the hierarchy, and calls for fidelity from the continent did not reverse the ebb tide. Toward the end of John Paul's papacy, Catholic intellectuals were sounding frustrated, and eager for new ideas from Rome on how to connect with a culture radically transforming from rural to urban.

"We are living in a theological winter, waiting for springtime," said Renold Blank, a theologian at the Pontifical Seminary of Sao Paulo.

Many Latin bishops were "afraid to speak in a loud voice" about needing redirection, said Luiz Alberto Gomez de Souza, research director of the Brazilian bishops' conference.

They did dare to hope, however, that one of their own might succeed John Paul. Among the prospects were Cardinal Oscar Rodriguez of Tegucigalpa, Honduras; Cardinal Claudio Hummes of Sao Paulo; and Cardinal Jorge Mario Bergoglio of Buenos Aires, Argentina.

When white smoke puffed above the Sistine Chapel on April 19, 2005, a theologian with a profoundly European worldview, the German Cardinal Joseph Ratzinger, was pope. Bergoglio was rumored to have placed second.

Benedict XVI has not publicly focused on the continent. Of the 15 new cardinals he named in March, only one was from Latin America.

"We've been overlooked again," said Allert Brown-Gort, a Mexican native and associate director of the Institute for Latino Studies at the University of Notre Dame.

Some changes, though, wait for no pope.

Even without the Vatican's imprimatur, the Catholic charismatic movement appears to be burgeoning throughout Latin America. Adherents of this emotive, hands-in-the-air hybrid could number more than 75 million, according to a well-regarded 2002 study by Gaston Espinosa, assistant professor of religious studies at Claremont McKenna College near Los Angeles.

Nearly half are in Brazil, where the flamboyant Rossi is the movement's rock star. Espinosa found that 500 priests countrywide were involved in charismatic worship.

That is a small subset, but a big sign to other clerics who, if grudgingly, see in it the best hope for Latin Catholicism.