Minutes after entering Mount Pleasant's Centro Catolico medical clinic, a young woman named Melissa Turner meets the emaciated Salvadoran man for whom she will translate all day. Almost too weak to talk, plagued with mouth sores and coughing, he tells her in Spanish he has no cash for a doctor. The two drive to a hospital, looking for a specialist who can diagnose the man gratis. A physician they meet immediately admits the man to the hospital.

Turner learns later that the Salvadoran was diagnosed with lymph cancer and put on chemotherapy. Not every day at the clinic brings such a crisis, Turner says, "but I do feel everything I do there is essential."

Melissa Turner is not a professional; she's one of many area volunteers who fill key roles for area clinics. Washingtonians also donate time in a range of other activities, from visiting hospices to answering hot lines to scrubbing bathrooms in housing rehabilitation projects.

But while more District residents than ever are volunteering, some who work in less-dramatic fields wonder if their labors have any effect. Across town from the Mount Pleasant clinic, for instance, a volunteer who rehabs low-income apartments says it can be hard to keep sight of his goal. "Sometimes people don't understand why you're out there," he says. "It can be frustrating, feeling, 'I don't see why we're out there hauling trash when no one is helping.' "

More than 98 million Americans, 23 percent more than in 1987, gave time to charitable causes in 1989, a new study shows. Their efforts, which add up to 20.5 billion hours and a monetary value of $170 billion, do indeed aid social causes, local activists say. But the activists -- who shelter the homeless, treat the indigent sick, and lobby for poor people on Capitol Hill -- differ over how volunteers help most.

"I think volunteers provide the real heart and soul of solutions to social problems," says Carol Fennelly of the Community for Creative Nonviolence (CCNV) shelter. "Money can deal with food, buildings, and you can buy a certain amount of compassion ... but the volunteers are here because they are truly committed to being here." And if gold coins rained down on the CCNV, Fennelly insists, volunteers would still staff the shelter, now managed by 50 full-time volunteers, some residents, and numerous part-timers. The CCNV, which advocates private/public cooperation against homelessness, occupies a publicly owned building and recently fought to put a controversial "right to shelter" referendum back on the ballot. The 1,400-bed shelter always is full.

Ironically, CCNV volunteers often do best where they're least comfortable. "The hardest thing for volunteers to do is to come in and relate to people in our building," Fennelly says. Volunteers, she says, "want a task to do, but our residents love it if people come in and play cards and listen to their stories."

Volunteers also help at the Washington Free Clinic, which employs a handful of paid staffers, says executive director John Clark. "One of the great advantages of using volunteers is that they can take time to teach people how to take care of their bodies and how they work," he says. "We can offer upwards of an hour, an hour and a half for an adolescent's first gynecological exam."

Another believer in community service work, from a different angle, is the Children's Defense Fund (CDF). A staunch promoter of national child-care, immunization, and "preventive investments" such as Head Start, the group believes "volunteerism has a role in many areas, but it's not by itself going too far in resolving any of these problems," spokesman Clifford Johnson says. Nevertheless, CDF actively supports a congressional bill called the National and Community Service Act.

True, the $120-million bill doesn't promote volunteerism in its purest form. Instead, as part of the proposal, disadvantaged adolescents would receive stipends to work on community projects such as construction, urban renewal and care for the elderly.

The program explicitly aims to help the young workers. "A properly designed youth-service program can help disadvantaged young people a great deal," Johnson says. "It's an important opportunity for them to acquire skills, discipline, a stronger sense of self-esteem and greater exposure to the world around them."

Often, in fact, volunteers' most substantive work is internal, organizers say. They're not just talking about a warm feeling of helping. More and more volunteers, coordinators observe, want a sense of community, an antidote to poor government, or empowerment in a frightening society. "I've had a lot of people call me and say, 'The whole city seems to be out of control -- what can I do?' " says the Volunteer Clearinghouse's James Lindsay. "Five years ago there was no need for people to come out and say those things."

For members of the African-American fraternity Alpha Phi Alpha, Inc., volunteerism means self-help, says member Eldridge Allen. His chapter, Omicron Lambda Alpha, participates in "Go to High School, Go to College," a national fraternity project, by tutoring and mentoring boys at Southeast's Ballou High School.

"It's always said, 'Start with home, with what you know best,' " notes Allen, who graduated from Ballou himself and now works in Citibank's Community Development department. The program "works for the simple reason that we identify a problem of our own instead of waiting for someone to do it. We identify ourselves as professional black men and we want others to follow."

But volunteers are most useful of all as social critics, asserts Brian O'Connell, president of a national nonprofit coalition called Independent Sector. Publicizing "criticism, outrage and reform" is a volunteer's single best service, says O'Connell, whose group urges Americans to give five hours a week and 5 percent of their income to charitable causes. The National Mental Health Association, O'Connell maintains, is advocacy at its best. Accepting no government funds and largely volunteer-staffed, the group is devoted to educating lawmakers and community members about mental health.

At the same time, it's dangerous to overestimate volunteerism's strength, some activists say. According to Independent Sector, the ratio of nonprofit to government spending is about 1 to 10. On a practical level, this means some activists suspect recent volunteerism drives by the government is just a matter of passing the buck.

"I can't help but be sort of sarcastic about the 'thousand points of light' concept. The people that I think George Bush was addressing aren't the kind of people who end up volunteering for us," says the Washington Free Clinic's Clark. Located in Columbia Heights, the clinic serves poor minority clients, and relies almost wholly on volunteer doctors, educators and staff.

"There's such a demand for this kind of health care that the fact that volunteers have to provide it says a lot about the health-care system not only in D.C., but nationwide," Clark says. "It strikes me as kind of sad that in the area of health care we have to rely on volunteers to do this kind of work."

A spokesman for the president's Office of National Service, however, argues that Bush's "thousand points of light" metaphor, first heard in his acceptance speech, is misunderstood. "It has nothing to do with displacing government's role in addressing social problems," Clark Ervin says. "We believe that at the heart of drug abuse, hunger, and illiteracy there are some material needs. But we really think all those problems are symptoms of larger, more fundamental causes," which only can be repaired by helping relationships among all sectors of society.

And, paradoxically, cutbacks in social programs have given volunteers a clout as never before. "I would characterize volunteerism as probably the last safety net we have in this society," says James Lindsay of the Volunteer Clearinghouse, located in a small, crowded office where volunteers are matched with more than 700 nonprofits. "In the last 10 years, social programs have been cut at least 35 to 45 percent. In many situations, volunteers are picking up the slack."

Alongside traditional activities, new volunteer trends -- and achievements -- have surfaced. The change can be read in sheer numbers, especially among baby boomers and blacks. But volunteerism's shape is shifting as well. "It's not individuals, but groups who are volunteering together -- schools, corporations, fraternities are getting involved," Lindsay says. "Most of the people we recruit work from 9 to 5. Fifty-six percent work every day, and 10 to 20 percent are full-time students. What we're seeing is that more people are likely to go together with friends or colleagues."

New organizations tailored for group volunteerism have sprouted in Washington and other cities. Area nonprofits, meanwhile, are scrambling to use the new labor force efficiently, finding projects for weekends, mornings and evenings. The Washington Free Clinic, for example, recently received a new paint job from members of doingsomething, which offers group activities one Saturday each month.

While group volunteering lacks the intimacy of one-on-one work, it can accomplish feats too vast for a single worker. At Sursum Corda, a housing project in Northwest, weekend "work parties" of 35 or more have hammered and scrubbed the battered apartments into marketability. By 1988, absentee management had left Sursum Corda so decrepit that HUD deemed the complex unsalable, says Sister Diane Roche, the resident manager. Raw sewage splashed through ceilings into the dining rooms below; so few apartments generated cash, Roche recalls, "that I remember just standing in a plumbing showroom once and crying. I wanted to buy two toilets and we only had enough money for one."

Since October 1988, however, work parties from churches, volunteer groups and civic organizations have descended on Sursum Corda three Saturdays a month. Although a typical group works only several hours each month, the number of participants magnifies the impact. The results, Roche says, "are astonishing." Ninety-six percent of the units are occupied, the complex's cash flow is excellent, and the tenants are close to fulfilling their long-standing goal of buying Sursum Corda themselves. "There's an energy larger than any single individual when groups get together," Roche says. "We could never have made this into something worth owning by ourselves."