The rite, those few priests who have performed it say, can unfold as a quiet prayer session or a show of violence.
The afflicted person may curse the cleric, speak in a voice not his or her own, even assume facial features that one priest described as "reptilian."
With some parishes seeing an increase in claims of demonic possession in the United States, the Roman Catholic Church is training its clergy in how to respond to requests for the ancient rite. More than 100 bishops and priests attended a November workshop on the subject in Baltimore.
Bishop Thomas J. Paprocki, who organized the two-day, closed-door event at the Baltimore Marriott Waterfront, says pastors need help discerning the difference between those who need an exorcist and those who only believe they do.
The goal, he says, was to help the clergy counsel people who believe they are possessed by a demon by referring them to a physician, a therapist, or — in very rare cases, he stresses — an exorcist.
"We have only a small number of priests who have any training in this area in the United States," said Paprocki, who heads the Diocese of Springfield, Ill. "Every diocese should really have its own resources."
While no one is keeping statistics, he says anecdotal reports suggest that the phenomenon of people claiming to be possessed "seems to have increased in the last five years or so."
Clergy and theologians offer several possible explanations: the growth of the Charismatic Renewal Movement, with its traditions of mysticism and ecstatic worship; renewed interest in the occult, abetted by the Internet; the influence of television shows about the paranormal and the many cinematic descendants of "The Exorcist," the 1973 film that spiked modern interest in the subject.
The burgeoning number of Catholic immigrants from Latin America and Africa, where belief in demonic possession is common, also has been suggested by some theologians as a possible factor.
At least one opinion survey suggests that substantial numbers of Americans believe in the possibility of demonic possession. A 2001 Gallup poll found 1,012 people split in their belief in demonic possession; 41 percent believed and 41 percent did not.
Paprocki estimated that about 30 of the 195 Catholic dioceses in the United States have appointed exorcists. The U.S. Conference of Catholic Bishops does not keep statistics, a spokeswoman said, as dioceses keep their exorcists' identities confidential.
The Archdiocese of Baltimore has not appointed an exorcist, spokesman Sean Caine said. He said he could find no record of the rite ever having been performed here.
"We have four priests in the Archdiocese who have experience, and who can investigate cases of paranormal complaints or suspected demonic activity," Caine wrote in an e-mail. Of the "very few" recent cases they have investigated, he said, "none required an exorcism."
The Baltimore event was the first Paprocki knows of to be sanctioned by the bishops' conference, and the number of attendees suggests to him that interest in demonic possession is strong. Paprocki, who chairs the conference's Committee on Canonical Affairs and Church Governance, said he was "pleasantly surprised" when more than 50 priests and more than 60 bishops turned out.
While exorcism has attracted both popular interest and official attention in the decades since the reforms of the Second Vatican Council in the 1960s, some Catholic theologians despair of the very subject as an anachronism that focuses on the devil rather than Jesus.
Thomas Groome, a theologian at Boston College, called the Baltimore session "a very peculiar event."
"The reality of evil in the modern world is patently obvious," he said, but recourse to supernatural explanations seems a "throwback" — and a convenient scapegoat.
He cited comments by Pope Benedict XVI blaming demonic causes for the emergence of the clergy sex abuse scandal in Europe.