About 160,000 people congregated at Harvard this weekend for an unusually quiet Head of the Charles, with only one arrest and no injuries reported.

The crowd was slightly smaller than last year, when 200,000 came to watch the annual regatta.

"It's getting a little better each year," said State Police Lt. Tom J. O'Laughlin, who was patrolling the riverfront yesterday. "It's been very good."

The arrest, made Saturday night by Harvard police, was for drinking in public and "possible possession of narcotics."

Bob A. Soffa, station supervisor of the Red Cross Emergency Aid Stations, said yesterday that there had been no illnesses or serious medical incidents, other than a sprained ankle.

"This is usually one of the better events of the year for us," Soffa said.

Students and visitors attributed the relative peace and quiet to a strong police presence.

"They [crowds] are a lot tamer," said Andrea B. Ellin, a native Bostonian who has attended this event for many years. "Two years ago you'd have a party at every corner; now it's more commercial and political."

While Head weekend featured some of the traditional partying, students said Harvard's security measures put a damper on the festivities.

"It got really congested and the T was just horrible," said Bora Chung '95. "You also had to show your ID everywhere and I was annoyed."

The gates of Harvard Yard were locked from 4 p.m. Saturday afternoon until 7 a.m. yesterday morning, and only people with Harvard ID's were permitted to enter. At the river houses, security personnel guarded each house.

"It was understandable," Chung said. "They are making more efforts to keep everything in order."

Other students avoided the party scene altogether, despite police efforts.

"I didn't even go outside, so I don't know what it was like," said Jennie M. Cheung '98.

But yesterday, onlookers were out, enjoying the peace and quiet. Robin A. Sacco, a visiting 1994 Cornell graduate, applauded Harvard's security efforts.