Washington, no one has to be told, is a city of museums. It's also a city of docents, the people who tell you what's what at all those museums.

Last year, 884 volunteers donated more than 85,730 hours as Smithsonian docents. Although most museum guides are not paid for their work, they tend to be equally enthusiastic about two compensations: the chance to teach and to learn.

While specifics vary, museums look for these qualities in their docents: a strong interest--not necessarily education or experience--in the area to be covered; a love of learning; a love of teaching (the word comes from the Latin docere, "to teach"); ability to meet the public and the stamina to stand and talk for several hours a week while giving tours. Fluency in a foreign language is welcome. All programs provide assistance in teaching techniques and ongoing training on the subjects.

"It's a labor of love," says Lois Young about her job as docent at the Hirshhorn Museum. "I get to do something that combines my background and experience--as artist, elementary-school teacher and mother--with my first love, modern art."

Like most docents, Young puts in much more time than the Hirshhorn's required three hours a week and twice-monthly training sessions.

Training at each institution varies. For example, the Hirshhorn (filled for two years) requires three months' in-depth training, plus a current university art course at the volunteer's expense. At the National Museum of Natural History, training involves one day a week for six weeks in the fall, and then once a month the rest of the year.

Some institutions educate docents in all areas covered by their museums. For instance, Corcoran docents are taught how to conduct eight tours, from "Discover America" to photography, and are briefed on special exhibits for teaching both in the museum and in outreach programs at schools and at senior-citizen homes. The 300 docents at Natural History each specialize in one area, such as dinosaurs or western civilization.

"The docent program," says Young, "has a degree of professionalism the likes of which I never thought could exist. I don't feel like I'm doing a volunteer job. It's a privilege."

After three months' training at the Hirshhorn, Young began giving tours in February to "walk-in" visitors.

"We, too," she says, "learn from the visitors who often have either a strong interest or background in modern art. But sometimes we have visitors who don't want to be there, who have accompanied a friend, or who are on a tour. Modern art is a mystery to them. That's a real challenge, to make them feel comfortable."

Washington-area docents are as varied as the museums they serve. Among them: teachers, nurses, flight attendants, physicians, a psychiatrist, bankers, retired persons, pilots, housewives with young children, military personnel, writers, an actress, artists, Hill workers, NASA and State Department personnel. For docents who have another full-time job, weekend work and evening training hours are available.

The vigorous docent training and experience often open doors to new career opportunities. Barbara Matteo, now assistant curator of education at the Corcoran Gallery of Art, "discovered museum education" as a docent at the Hirshhorn and Corcoran.

Jan Levine, 46, a former teacher and a docent at the Hirshhorn since its opening in 1974, has parlayed her training into work as an art-education consultant. "Without my years of volunteer service," she says, "I would not have been able to reenter a profession I love."

Her husband, Dr. Howard Levine, 47, also is a Hirshhorn docent. Last year he combined his work and his "diversion" to write a paper, "Raoul Dufy, The Treatment of His Arthritis and the Effect on His Art," which won an award at the 15th International Congress of Rheumatology in Paris. He and his wife often exchange ideas on particular works.

"It's a way of sharing," says Jan Levine. "I don't play tennis, or golf, or doctor. It's a beautiful ongoing learning experience."

Former pilot Bill Tinkler, 53, became a docent at the National Air and Space Museum six years ago because he "enjoyed discussing aviation." When he retired from the airline, his docent job grew.

"Today it is practically a vocation," says Tinkler, who specializes in adult tours. "I'm constantly aware that I get a lot out of it." "You have to be very careful. In your group may be the person who designed the aircraft."

Says avowed "airplane nut" and Air and Space docent Ken Robert, 39, who is with the Defense Department, "It's rewarding to have a buff ask a technical question and you can answer it, but it's equally rewarding when a spouse comes up to you after a tour and says, 'I had a really good time.' You just can't buy that kind of satisfaction."

Carol James, 53, got involved at Air and Space when she was "bogged down with a little boy hanging off each leg and a couple of teen-agers." Presented with a choice of a docent's position in American history or at Air and Space, she asked her then 6- and 7-year-old sons what she should do. "They shouted 'Air and Space!' "

Thus began James' 11-year docent career. She specializes in "The Discovery Tour" for kindergarten through third-graders and also writes and edits a newsletter, "The Paper Airplane."

Although docent programs are known to be highly competitive, all institutions encourage applications. Some fill vacancies year-round; others recruit only when there is a need, or once a year, often in the summer, with training beginning in the fall.

"We are," says Jenna Blalock, 39, docent at the Museum of Natural History, "treated like co-workers."