"The mixing of boys and girls is so ubiquitous in American society, most priests don't see a reason to draw the line here," said Kenneth A. Briggs, who recently visited Catholic churches around the nation for research on a book called "Holy Siege" (Harper San Francisco, 1992).

By his estimate, 1 of 4 Catholic churches nationwide uses girls at the altar for at least some Masses. Even in a church where many women accept that they cannot serve as priests, Mr. Briggs said, they want their young daughters to have equal rights.

By some estimates, the practice of allowing girls to serve may have declined somewhat from a peak a decade ago. In 1985, reflecting that movement, the Catholic bishops of the United States asked the Vatican to lift the ban on altar girls. While the Vatican has yet to act, most bishops tend to "look the other way," Mr. Briggs said. In some rare cases, like in Rochester, the bishop has publicly condoned their use.

"This grows out of our experience and understanding of what we see as the role of the church," said the Rev. Michael F. Conboy, pastor of St. Joseph's. "There are times when the practice of the faith precedes the rules and regulations."

Father Conboy has the support of the head of the Rochester Diocese, Bishop Matthew H. Clark. In New York City, however, where theologically conservative bishops hold sway, altar girls serve without fanfare, making it difficult to say just how widespread the practice is. On two occasions, reflecting an atmosphere of discomfort, priests who do allow altar girls asked that a reporter and photographer not visit. "We can't go public," one priest said. "If we do, we won't have altar girls anymore."