Most of the mothers and fathers at the meeting are in their late 30s, with their eldest children in high school. They live in a subdivision near New Hampshire Avenue in Silver Spring where large, two-story houses are set back on broad green lawns. The summer evening breezes carry the scent of two kinds of grass -- from the freshly mown lawns, and marijuana smoke from around the neighborhood pond.

The group of a dozen or so neighbors had gathered in a member's basement rec room to hear a psychiatrist address a subject that has struck fear and guilt in a generation of parents: teen-agers' use of alcohol and drugs.

Their organization, called a parents' peer group, is one of dozens in Montgomery County and among hundreds in the Washington metropolitan area. They have been formed within the past year to help parents lend emotional support to one another and find the strength in numbers to discipline their sons and daughters.

To their teen-aged children they are a snoop group, a spy group, a lynch mob, vigilantes and "a few other choice names," says the Silver Spring group's organizer, Carolyn Burns. "Particularly because I was active, my son told me he got a lot of flak at school. He told me several times I had ruined his life."

The parents say the impetus for forming a "peer group" usually comes from a discovery of paraphernalia in a teen-ager's room, or other evidence of drug use. Then comes a realization that attitude changes they had attributed to the normal upheavals of adolescence more likely were caused by marijuana smoking or other drug use.

One typical reaction to such a discovery is to telephone the parents of the teen-ager's friends and arrange for an organizational meeting.

Burns called that first meeting of parents in her neighborhood last October, when whe suspected that her son may have smoked marijuana. She jotted down the names of her son's friends, and soon had a list of 30 contacts. jShe keeps a list of parents' names on her kitchen counter. The adults phone each other frequently, and a core group of 12 meets regularly.

Burns' group invited local experts to talk with them about youth problems. They discussd discipline and drew up rules and the consequences of infractions. All the parents agreed to enforce the code with their teen-agers. Among the rules: Confinement at home for a weekend for violating curfew, or confinement for a whole week for smoking pot or drinking.

Burns explained why parents need to by united behind a uniform code of behavior: "At a time (teen years) when parents quit talking to their kids, the kids are talking more and more among themselves. It becomes almost impossible to enforce discipline if you are doing it alone."

If Burns' son says he is going to a party, Burns telephones the home to verify that a party is planned, that it will be chaperoned, and that there will be no alcohol or drugs.

During the night after that first Silver Spring meeting, youths in the neighborhood placed a dead rabbit on Burns' car.

Many parents interviewed at peer group meetings were reluctant to be specific about problems with their children. Many others said they had seen no evidence their teen-agers were using drugs, but they came to the meetings in the hope of learning how to keep them from starting bad habits.

The success of a parents' group is difficult to gauge, however. Only a handful of members can point to concrete proof of effectiveness. "We can't see what we've prevented," says Burns. "The parent peer group has been helpful mostly to the parents, because it's given us a caring bond, a base from which to work. Parents feel closer to their children because they're more understanding of the problem."

At one recent meeting, however, the parents sounded discouraged. "You spend half your time trying to figure out if they (teen-agers) are conning you," said one mother. "It's frustrating trying to force someone to do something they don't want to," said another.

"Why don't we smoke pot?" another member said bitterly. "There's more pressure on us than on them."

"There is some discouragement because -- of course -- we all want a miracle," said Carolyn Burns later. "But we're encouraged because we've made many new friends and the situation at home has improved. . . We're more aware of the problems that our teen-agers have to deal with and the way they live."

A Rockville woman who organized parents in her neighborhood last winter, after her husband found their 13-year-old son "flat out, zonked," and suspected he had been using marijuana. She said belonging to the group forces her "to be aware of the problem and to do something about it . . . When you see signs of change (in children), you have to do something about it. It's everywhere out there and you can't take the blame for it."

"Kids are very concerned about what other parents think of them," said her husband. "Suddenly they're being exposed, and they're not innocent little guys. They can't give a song-and-dance routine.

"But each parent looks at it from a different viewpoint. Some people stopped coming because they felt that others' problems were worse than their own. But their kids are pulling the wool over their eyes. We're upset over that. We think their problem is worse."

The mother said she wishes she had discovered her son's drug problem three years earlier. "At age 13, it happened overnight . . . he became a teen-ager overnight."

"One high school girl said she had 42 drinks a week," the woman continued. "My (16-year-old) daughter admits to two drinks and a hit off the bong. Teen-agers aren't handling their anxieties. They're hiding in pot . . . Kids take 50 cents to school for lunch, put it together and pass marijuana around. These are 8-year-olds. It's well entrenched by the time they get to high school. It's down to the fifth grade now."

Recent statistics bear out the mother's concerns. Montgomery County public schools participated in a statewide survey of student drug use for the first time last year. The results, in part: 9 percent of eighth graders in the county's schools, 25.5 percent of 10th graders reported they were using marijuana. The survey also found the average age at first use was dropping.The high school seniors said they first smoked marijuana at 14; the eighth graders put it at age 11.

Teen-agers insist the parents' organizations are ineffective, and their initial anger over their formation has turned to disdain. A group of Paint Branch High School students, some of whose parents have attended peer-group meetings, discussed the parent gatherings recently.

"It gives them something to do," said 16-year-old Lisa Gropper. "They think theyhre helping and it makes them feel like they have some authority. They talk about going through our purses or listening in on our telephone conversations."

"The greastest effect is among the parents. Knowledge makes them feel better," said Danny Schweitzer, 18. "They could be successful in stopping younger kids, but high school kids are too old to be told what to do."

"It just makes us sly," said Holly Hone, 16. She said her parents came home after one meeting and told her that the next time whe overslept on a school morning, she couldn't take a shower that day or the next. "That didn't last long," she added.

"They're just giving you hassles," said Matt Gallagher, 17. "They look for things. Every time you walk through the door, it's like an inspection."

John Rumbaugh, 18, an Einstein High School senior whose mother, Rita Rumbaugh, is a coordinator of parent peer groups in that area, said when he first heard about the groups, "I was mad because it was like a group coming after us. What I felt was wrong was that they got together and supported each other, but I had no one supporting me."

"It's kind of embarrassing. It's like she couldn't trust us and was checking up on us," said his sister Katie, 17.

"Even if I wasn't doing anything, if someone looked at me like I was doing something wrong, I'd get all jittery," said John, who will go to the University of Maryland on a soccer scholarship this fall. His mother describes him as a model son.

Newport Middle School principal Robert Redmond says much of the youthful resentment could be avoided if parent groups were formed early, and he is working toward that goal. He has been directed by the county school system to spend 40 percent of his time organizing the peer groups, and he is encouraging the parents of elementary and junior high students to get together.

Russell Wallace of the Rockville Neighborhood Youth Services, who works with parent groups in the Rockville, area, acknowledged that cracking down is "definitely tough. Grounding the kids grounds the parents as well." But, he added, "In a couple of families, I think there's been result, though. There is less (drug) use. One thing it (organizing) does is introduce the idea of doubt or guilt to the kids. Parents are saying, 'you're not going to ruin your life and we're going to see the you don't.'"

Teen-agers who were asked why they thought their parents formed a group at first were silent. Then one answered, "Paranoia." Another added, "They're worried that we're going to die."