Lonise Bias, mother of Len Bias, had just finished a speech at Northern Virginia's first "Rock Against Drugs" concert and was heading toward the Woodbridge Senior High School parking lot Friday night when a young man called out in the darkness.

"My name is Lenny; I'm the one who wrote you the letter," the man said after asking for Bias' autograph. After a brief conversation, the two embraced.

Lenny and Bias shared something more than a brief moment. They both knew the tragedy of drugs, specifically cocaine. Bias had seen her son go from being an All-America basketball player at the University of Maryland and soon-to-be-millionaire with the National Basketball Association's Boston Celtics to a body "stretched out on a concrete slab," in the words she used.

Lenny, who declined to give his full name, said he almost lost his life to cocaine and admitted to once selling the drug to others, but he said he is no longer involved with drugs after spending time in a rehabilitation program.

He said he wrote the letter, in which he described his involvement with cocaine, to show Bias that he had begun to understand her message against illegal drug use.

It was an unlikely combination, the mother of the fallen basketball star and the former drug pusher, in an evening of contradictions. What brought them together was the concert, sponsored by the Prince William Crime Prevention Council, to entertain and inform about the dangers of drugs.

Lean, long-haired members of the bands, Misfit and Bad Habit, played almost deafening rock music as an audience of 600 energetic youths, stiff-jawed police and slightly balding and overweight parents listened.

"I'm not a rock fan," said Yvonne Sullivan, a 47-year-old member of the council, made up of police, businesses and more than 100 neighborhood groups. "I think it is pure junk. But I think this concert is good because it points out that there can be rock music and fun without drugs."

At 11 p.m., teen-agers Mary Green, Kerry Katicich, Theresa Wilson, Michelle Fleming and Brenda Abbott were dancing in unison back and forth on a walkway about the gymnasium floor.

"Oh yeah," said Mary, 16, while applauding the Misfits. The band members "were kicking," she said.

"I think this is great," said Mike Waterhouse, 17. "I think there should be more of this for us. All of us love to party. But some want to party the other way {with drugs}. But partying for me is just jamming and having fun."

The county's drug problem is no worse than in other Northern Virginia localities, said Roger Barton of the Prince William County police. "If you want it, you can get it. We're just trying to get kids to say no. It sounds simple, but it's not that easy," he said.

Since her son died, Bias has made more than 60 speeches to thousands of youths in locations as distant as Rapid City, S.D., and Hawaii.

She encouraged parents to be involved with their children and pleaded with the teen-agers to "love themselves" and not to succumb to peer pressure.

"It is not all right to go along with the group all the time," Bias told the crowd as she spoke from the center of a basketball court similar to many on which her son had starred. "Everyone that grins in your face is not your friend. Peer pressure destroys. Peer pressure kills."

Lynda Parks, a 14-year-old sophomore at Woodbridge, said, "The band was really good, and I think Mrs. Bias was really trying to get a message across, and I think she did. I was listening."

Garry Jenkins, 35, of Stafford County watched Bias with more than passing interest. "You get the kids together, it gets them off the street," said Jenkins, who is raising two children, Shannon, 10, and Sean, 14. "It's their kind of music, something they can relate to . . . . Everybody says, 'My kid won't,' but you never know."

Jenkins, who drives a tow truck, said he sees accidents firsthand and that many of them are the result of youths high on drugs or alcohol.

"You can't just sit back and tell them that 'you can't do this' and not help them find something else to do. When I grew up, the YMCA had a party every Friday night," Jenkins said.

Bias, who Jenkins described as having "more heart than anyone" he had seen, said parents and youths need to learn from each other and pay attention to each other.

Lenny, the letter writer, said that he and a friend "tried to sell cocaine to get rich, and it got us. The drug takes them down every time . . . . This is not a joke."