The homecoming for Rockville's O.A.R., a rock band headlining for the first time at Wolf Trap last week, featured a performance that its manager called "probably the best show of their career."

But the joyous concert had an unfortunate coda: When it was over, 46 people in the crowd of more than 7,000 had been cited for underage drinking, and a handful of additional arrests were made on charges of marijuana possession and other misdemeanors, Fairfax County and U.S. Park Police said yesterday. Those arrested ranged in age from 15 to 22.

Many of the arrests were made by uniformed Fairfax bicycle patrol officers in the parking lots outside Wolf Trap, both before the Aug. 10 show and during intermissions. The busts were part of the Fairfax department's efforts to combat underage drinking.

Fairfax police issued 26 misdemeanor summonses for underage drinking, all but one in the parking lots, county police spokeswoman Mary Mulrenan said. Fairfax also charged three people with misdemeanor possession of marijuana. Two of those were inside the amphitheater's grounds.

Park Police charged 20 underage people with illegally possessing alcohol, Capt. Jeanne O'Toole said. In addition, one person was charged in four pickpocket robberies, another person is being sought for purse snatching and two people were charged with urinating in public.

"That's pretty high," O'Toole said of the numbers, comparing them with other Wolf Trap shows. She said a Park Police supervisor who handled the concert called it "one of the worst he's worked, in terms of rowdiness."

Dave Roberge, who manages O.A.R. and heads the independent record label Everfine Records, said: "That's extremely disappointing. . . . The band's message has always been about unity and positivity. And over the years, we've really noticed the crowds have gotten much rowdier," even though band members discourage crowd surfing and sexual harassment, and the band's own staff "will eject people for underage drinking."

O.A.R., which stands for "Of A Revolution," has a national fan base and has become one of the top 40 touring bands in the country. The group was looking forward to the Wolf Trap show in particular because four of the five members met and started playing in Rockville, and this was their first time playing the amphitheater.

But police were also anticipating the show. For the past three Wolf Trap seasons, Fairfax police have met with Park Police and Wolf Trap officials in the spring to preview the schedule and determine which bands -- and their audiences -- might present the biggest "challenges," park Director William Crockett said.

Wolf Trap has slightly different security considerations because it allows patrons to bring alcohol and coolers onto the lawn and lets people leave the venue and return during performances. One of the main considerations, Crockett said, is whether a band might attract a younger crowd.

"When you see somebody 16 years old go out of here in an ambulance," Crockett said, "it makes you want to cry."

Roberge acknowledged that many young fans need medical help at O.A.R. shows, and the band is baffled. "It's so bizarre to us because we don't promote that," he said. "It's scary. Is alcohol necessary to enjoy the show? We don't think so."

Crockett said no decision had been made on whether to allow the band back. A rejection would be particularly crushing to the band, Roberge said. "Wolf Trap is one of the venues that we wanted to be invited back to."