The throngs that filled Arlington's Crystal City Marriott yesterday hailed from most every public service profession -- police officers, schoolteachers, social workers, sheriffs, elected officials -- from every jurisdiction in the Washington area.

But they gathered with a single purpose: defeating gangs.

About 500 people -- far more than were expected -- showed up for the first Regional Gang Summit, organized by the Metropolitan Washington Council of Governments.

A regionwide summit on what has become one of Washington's most prominent public safety issues was needed because gangs know no jurisdictional boundaries, said David Robertson, COG's executive director.

"The manifestations might be different, but at heart, gang violence is the same in one community as it is in the other," he said. "The gangs might go by different names, but they all share commonalities."

A major aim of the conference was to provide a forum for sharing information on how different municipalities address gang violence, said Fairfax County Supervisor Penelope A. Gross (D-Mason), who was a principal organizer along with Arlington County Board member Walter Tejada (D).

"Sometimes we try to replicate each other and don't even know it," Gross said. "We put all these resources into a program and don't realize that it didn't work well in another jurisdiction."

The information exchange seemed to work throughout the day. At one late-afternoon session, Joe McGrath, a gang investigator, and Chris Edmonds, a juvenile probation officer, described an Arlington program that shares information between their departments. That has helped patrol officers keep an eye on gang members at public schools.

Light bulbs seemed to turn on above the heads of several people in the audience. Three parole officers from the District began peppering McGrath and Edmonds with questions about how they set up their program and how often the two departments meet.

"It's one of the more successful mini-conferences I've been to," said Arlington County Board member Jay Fisette (D), who listened to the presentation. "It's because of the cross-disciplinary dialogue that is going on."

Other officials described gang-prevention programs in middle schools and efforts to reach the parents of gang members. Several of the sessions instructed police officers about dealing with concealed compartments in vehicles and enforcing new gang laws. Those were closed to the public.

Rep. Frank R. Wolf (R-Va.) spoke about the rise in recruitment efforts by gangs in jails and prisons, saying it has become a major concern for sheriffs in Virginia. He said the FBI told him that gang activity has spread from Northern Virginia as far as Lynchburg, Roanoke, the Eastern Shore and Hampton Roads.

Rep. James P. Moran Jr. (D-Va.) added: "It's a problem that's getting worse and that needs to be addressed throughout the entire region. . . . In many ways, it's not too dissimilar [to] the war on terrorism. You've got to arrest and prosecute the leaders, planners and recruiters, but mostly you have to shut off the sources of recruitment."