The children are off to school, the toddlers are tucked in for a nap and Phyllis Katz and Sharon Butler sit down to their day's work. Clutter builds as they scatter files across the desk top searching for number 317, the 36-year-old, 5-foot-9 executive who likes music and children.

Butler thinks he'd be simply smashing with number 378, the attorney and concert cellist who wants a large family.

Katz and Butler are "shadchans," or matchmakers, carrying on an old and honored Jewish tradition from their neighboring homes in Wheaton. As proprietors of a Jewish dating service called Shalom Adventure, Katz and Butler, both observant Jews and mothers of three, are doing more than having fun and earning spending money. They believe they are making a contribution to Judaism by helping Jews marry within their faith.

"We were always running into people saying, 'Do you know anybody for me?'. . . Often we didn't know anybody," said Katz. "We feel stongly that Jews sould marry each other and we want to do something about it. Finally we came up with this idea," said Katz, who met her husband 12 years ago through a similar service.

So far they've arranged four to 10 dates each for approximately 400 area persons, said Katz, adding that at least five of those couples have married.

Although that figure may seem relatively low, Katz said she's delighted because "that's five more couples who wouldn't have married otherwise." She said it is possible that others have married but are reluctant to announce marriage plans by writing to a post office box number, which is how the service does its business.

Modern-day matchmaking is "absolutely necessary if Judaism is to survive," according Rabbi Stephen Listfield, who himself gives nature a nudge by holding singles sabbath services, brunches and Judaic studies courses at Adas Israel synagogue in Northwest Washington.

"Jews are a tiny minority . . . 2.7 percent of the population," said Listfield, who was not familiar with Shalom Adventure but likes the idea. "If a Jew wants to get married, they have a chance of 97-to-2 that it's going to be a gentile.

"Every marriage out of the faith lowers the number of Jewish people and reduces the chances of Jewish continuity. So I feel very happy to create conditions that enable Jewish people to meet, date and maybe marry each other."

Butler echoes that attitude, saying, "When you get the nice letters or find out somebody got married, it makes you happy." That happiness has been her and Katz's primary reward from Shalom Adventure so far. They say the service netted them a couple hundred dollars apiece last year, but expect to earn much more this year because of a rise in fees and applications.

A four-month membership in Shalom Adventure has risen from $7.50 when it opened three years ago to $18 and is offered only to single Jews.

Applicants are asked to fill out a questionnaire describing, among other things, their own and their desired match's physical attributes, degree of religious observance, musical taste and political feelings. They are also asked to write several paragraphs describing themselves and outlining what overall qualities are most important to them.

As applications arrive, usually 30 to 40 a month, Katz, a former teacher and Butler, a former rehabilitation counselor, check through the files by hand, matching age, height and common interests. Within six weeks, they say, applicants receive a form letter listing the names and phone numbers of potential dates. Applications are then filed according to age and sex to be used for future matches.

Katz, 34, and Butler, 30, have different approaches to their work. Butler, the romantic, gets a feel for the person and sometimes overlooks height or age requirements if she "feels" the overall match works. "You get a certain satisfaction when two applications look good together."

Katz said she is more likely to match very closely to the applicant's stated desires, "which isn't always easy," she said.

"Some people, ususally men in their late 30s, are looking for 'the virgin queen,'" said Katz, "someone who is beautiful, slim, makes a good living and has all the same interests. You know these people will never find anybody. You can tell by how stiff the applications sound.

"One sent a 10-page, single-spaced typed letter describing what he was looking for in a mate," she said.

Their work is loaded with surprises, they said. For instance, they hadn't expected to find the "under 30 male" file so crowded, said Katz, pulling out an inch-think manila folder bulging with forms. But the "over 40 male" file is skimpy.

Sometimes they return applications, such as those filled out by parents disppointed that their children weren't dating Jews, and a half-dozen from non-Jews. "We've even gotten an obscene application," said Katz, "which we returned with a letter saying we don't have anyone who fits that description."