It's a cold, rainy night, and the Pit is virtually deserted. The teenagers--many of them runaways or homeless--who while away their time across from Harvard Yard in the area next to the T stop have apparently gone on to find a warmer place for the evening.

A van announcing free medical services rolls to a stop outside the Pit, and the teenagers slowly begin to reappear despite the inclement weather.

The van is a familiar presence in the Square--it has been visiting this stop and others in Cambridge and Boston regularly for the last 30 years, and now comes to the Square every evening.

Few of its clients have physical problems requiring immediate medical attention. Instead, they come to the van for information about drugs, pregnancy or sexually transmitted diseases, and some come simply to talk to the volunteers.

"We are only the first step in health care," says volunteer Karen L. Perella. "We just want the kids to be comfortable in what is a non-threatening situation. We see them every day, so we can give them some much-needed consistency in their lives."

A Place of Their Own

At 7:30 p.m., the moment the van's doors swing open, a teenage girl steps right up, climbing eagerly inside. Her face brightens as she greets volunteers she has not seen in weeks. Following close behind her is a boy dwarfed by his enormous pants. They sit down together and soon begin to laugh with the volunteers about jobs and mutual acquaintances.

Suddenly, the girl realizes something important is missing.

"No hot chocolate today?" she asks.

The volunteers, who generally bring hot chocolate or sandwiches, shake their heads and promise to bring the coveted drink the next day. After a few more minutes of chatting, the teenagers leave the van, disappearing into the cold night without any mention of matters medical.

The van, separated into three separate spaces, is set up to allow such informal visits. The area where the hot chocolate is usually kept is designed for casual conversation. On one side is a brightly-colored collage of pamphlets, running the gamut from information about job opportunities to sexually transmitted diseases to a "street survival guide," listing places to find free meals or clothing. A large poster on one wall urges teenagers to "exercise your right to be healthy."

Van rules handwritten in red magic marker are tacked on the wall. The rules prohibit alcohol, drugs and violence in the van.

These rules are respected. The van is a police-free zone, meaning that the Cambridge police have agreed not to come into the van unless they are required to by an emergency.

"This helps the kids know that it's a place that belongs to them, so they need to respect it," says Maurice W. Melchiono, a nurse practitioner who volunteers with the medical van. "It's important for us to be able to foster a sense of safety for the teenagers."

A gray curtain separates the drop-in room from the part of the van where bandages and antibiotics are kept in locked cabinets.

Melchiono describes the care that can be given from the inside of a mobile medical van as "Band-Aid medicine."

"We deal with routine complaints like ear infections or sinus infections," he says. "We occasionally see some trauma, like someone coming in after they've been hit over the head with a beer bottle."

The van does not provide ongoing medical care. Instead, it is a "gateway to get kids from the streets to a primary care physician," Melchiono says.

"Many of these kids have long histories of abuse, so they are not trusting," he says. "We need to meet them where they're at."

Someone to Talk To

Because many of the van's clients have suffered abuse, visits often have a mental health component as well.

Melchiono remembers one particularly poignant visit.

"A patient came on and said she just wanted a blood pressure test, but I could tell that there was something more," he says. "It turns out she was exchanging sex for a place to sleep, and just wanted someone to talk to."

Melchiono says he believes that the program's effort to address more than just physical needs is at the root of its success.

"I've had people come up to me on the street in business suits and say thank you for the help we gave them years ago," he says.

And, Melchiono says, the trust must begin with the informal relationship that develops between the volunteers and the teenagers they see on a regular basis.

A girl steps tentatively into the van, saying that she thinks something might be wrong with her leg. As Melchiono leads her into the back room of the van, her friends begin to dance playfully outside, a further sign of their comfort with the volunteers.

"Why are you dancing out there?" Perella asks one of the boys.

"I'm not dancing," the boy answers jokingly. "I'm an actor."

They continue dancing and talking until their friend is ready to leave.

This sort of casual, comfortable relationship has allowed the free medical van to become a welcome fixture in Harvard Square. And for some, the van's nightly hour-long visit is an essential part of their routine.

Throughout the evening, an eclectic assortment of people--from purple-haired teenagers in leather to old men--stop by asking for hot chocolate, or for a sandwich, or just to say hello. Often the volunteers greet the people by name.

The sense of community among homeless youths that the mobile medical van has been quietly building for 30 years, Melchiono says, is just as important as the medical service the van offers.

He remembers when a homeless adolescent girl was hit by a car and killed. "We all had a memorial service for her, and I remember thinking that this is a girl with no family, but her family--her family of choice--came. I thought, what a wonderful example of a group of young people coming together to share their memories. I was touched."

An Intricate History

The medical van is just one service provided by Bridge Over Troubled Waters, a Boston-based organization established in 1970 to serve runaways and homeless youths. While the program targets people ages 14 through 25, the van does not turn away older people who need medical care.

The entire organization grew out of one book-mobile turned mobile medical van, which made regular stops anywhere homeless youths were known to congregate. The van was the first of its kind, and its success inspired activists nationwide to follow suit.

Today, the van is staffed solely by volunteers like Melchiono, who says he heard about the program 17 years ago and fell in love with it. He ran the medical van during the '80s and has been volunteering his time in addition to his regular job as a nurse practitioner with Children's Hospital in Boston ever since.

During their hour-long stay in the Square, the volunteers routinely see anywhere from three to 30 patients. Visitors are more numerous in the summer due to the general increase in Square foot traffic.

In addition to the Square, the van travels to the Park Street T stop, a Central Square homeless shelter, Copley Square and Chinatown.

The Square has traditionally been the busiest stop for the van, Perella says.

"It's amazing that right in the middle of Harvard University there are all these homeless kids," she says. "It's a different world."

And as he watches the teenagers walk away across the Pit, into the dark, rainy night, Melchiono agrees.

"It's a silent epidemic," he says.

He gestures across the street at the gates to Harvard Yard. "You wonder what events in life led to this dichotomy, to some kids ending up here and some ending up over there," he says.

At 8:30, only the volunteers are left inside the van. They will head to a shelter and then to Chinatown before finally calling it a night at 10 p.m.

"I love this," says Melchiono, as he surveys the bright van interior. "I think of these kids as teachers. They can teach us so much, if we only open our eyes and ears to listen. I just don't think we do enough of that."