A Christmas Mass was interrupted briefly yesterday when AIDS activists entered a downtown church to protest its recent decision to discontinue workshops for AIDS patients.

Tim McCarthy, a member of the AIDS Coalition to Unleash Power, or ACT-UP, said he was beaten by four parishioners of St. Mary's Catholic Church, 727 Fifth St. NW, while staging a protest with several others as Mass was being said in Latin.

The Rev. Aldo Petrini, the church pastor who was conducting Mass when the altercation broke out around 9:30 a.m., called the allegation that McCarthy was beaten "ridiculous." Police officers refused McCarthy's demands for criminal charges against the parishioners.

McCarthy and about six other members of ACT-UP, a confrontational group that demonstrates on behalf of AIDS patients, were protesting a recent decision by St. Mary's to end workshops in the church basement for AIDS patients.

"We had a group of people suffering from AIDS coming to the workshop and we saw it was going to be a problem," Petrini said. "A small number of the congregation complained." Petrini said the workshops -- conducted by Damian Ministries, a Catholic order that operates houses for people with AIDS -- were relocated by the Archdiocese of Washington.

"Our intention is not to ruin anyone's Christmas," Stephen Smith, a spokesman for ACT-UP DC, said before the protest. "We want to force the issue out into the open."

At least four ACT-UP members went inside the church and sat quietly throughout the Mass, witnesses said. McCarthy stood away from the protesters, taping the demonstration on a video camera.

The tape, played for reporters, shows one parishioner slapping McCarthy. The tape also shows the other protesters standing, raising placards and then leaving the church. At one point, several men can be seen approaching McCarthy, and there are sounds of a scuffle, including breaking glass and McCarthy screaming for help.

ACT-UP activists have disrupted services at St. Patrick's Cathedral in New York City to protest the church's teachings.

"I don't approve of them coming in to interrupt church," said a St. Mary's parishioner, Ramon Gomez. "They insulted us and they showed no respect."