It's 8 p.m. and Tiffany Gardner is lying on a couch, a telephone pressed to her ear.

It's a common scene for a 17-year-old whiling away a summer before senior year in high school.But Tiffany is at work and she is speaking to a stranger - an unmarried 19-year-old girl who recently had a baby.

"Her parents ignored her pregnancy and her boyfriend is away in the military," said the volunteer listener at Teen Line, a teen-to-teen hotline.

"She was just really depressed," Tiffany said. "She wasn't looking for advice, just someone to listen."

In the seven years since Teen Line began, more than 50,000 calls have come in to people like Tiffany, who was on duty during a recent night with three other teen listeners and an adult health care professional.

The listeners work out of Cedars-Sinai Medical Center in an office where nearly every inch of wall space is covered with referral numbers to hundreds of service organizations such as Planned Parenthood, Suicide Prevention, the Department of Child Services and AIDS information centers.

"When teens are in need, no matter what their socio-economic status, they contact their peers," said psychiatrist Dr. Terry D. Lipton, president of The Center for the Study of Young People in Groups and co-founder of Teen Line.

"They won't talk to school counselors, psychiatrists or priests, but what they will do is pick up the phone and call a friend."

Teen Line is staffed nightly from 6 p.m. to 10 p.m. Off-hour callers can leave a message and their call will be returned by a teen listener.

Most callers are between ages 13 and 19, although parents sometimes phone to get a teenager's perspective on problems their children are experiencing, said Elaine Leader, a senior staff member at Cedar-Sinai's Department of Psychiatry and program coordinator of Teen Line.

Most calls deal with boyfriend-girlfriend problems, but the listeners often hear from pregnant teens, those seeking sexual advice, and child-abuse victims.

From 3 percent to 4 percent of the Teen Line calls are suicidal, Leader said.

The volunteer listeners are carefully screened before being accepted, then must train 12 weeks before answering a hotline phone.

The training focuses on developing rapport, crisis intervention, addictive behaviors, all aspects of sexuality, family problems and more. The volunteers must attend either a recovery program meeting such as Alcoholics Anonymous or Overeaters Anonymous, participate in a Teen Line outreach program in Los Angeles high schools, attend monthly staff meetings and commit one night per week to the hotline.

Lipton, Leader and other adult specialists unaffiliated with the program have few reservations about allowing teenagers to take on the responsibility of suicide calls.

"These young people are in that position anyway," Lipton said. "On a daily basis they are in school with kids and peers who constantly give clues about their own despair."