Perhaps the brochure Harry Finley had printed up for his collection says it best: "The Museum of WHAT?"

The current exhibit features replicas of the first Kotex ad campaign. On the wall are samples of sanitary napkins, both the disposable kind and the new, reusable variety. There's a French magazine ad hanging from the ceiling in a plexiglass cover, promoting a tampon that comes in cheerfully polka-dotted applicators. Plastic torsos hang from the ceiling as well, dressed in belts and pads of different eras, ranging from the recent leopard-skin pattern to a replica of the 1914 rubber apron from Sears that tied around the waist and included metal weights around the hem.

Welcome to the Museum of Menstruation, or MUM, as in "mum's the word," housed since August 1994 in the basement of Finley's New Carrollton house.

Forget the hairball at the National Museum of Health and Medicine, forget the Potato Museum -- here's an opportunity for real education. There's no gift shop or snack bar, and it's open only by appointment, but where else could you learn -- if you had the inclination and could deal with the eccentric elements of the place -- that the word Kotex came from "cotton-like texture"?

By putting himself forward as the proprietor of the MUM, Finley knows he has set himself up for criticism -- not just from the menstrual crazies who paint with their blood but from experts who say, gently, that his collection is far from comprehensive and the location a bit unnerving.

"There are many academically-based researchers interested in the menstrual phenomenon; it's a growing field," says Jane Harrison-Hohner, director of the Menstrual Disorders Clinic at the University of Oregon's medical school. She visited the museum during a trip to Washington. "I think this is another manifestation of the interest, and it's great that he is taking on the taboo. But it's a shame his collection isn't more accessible. I think it would be better off if he gave it to a women's museum, or a medical collection."

Katherine Ott, a PhD under contract to the Smithsonian as a medical historian, sees the collection as having value as popular culture rather than scholarship. "Popular culture is just as important," says Ott, who visited the museum with some colleagues. "Americans are so prudish about bodily functions, it's good to have someone who will say the word out loud."

Finley is well aware that most people might not immediately embrace the idea of a museum devoted to a body function, and he understands that some are wary of a 52-year-old bachelor being its curator.

"The anger its {sic} stirred in our circle is enough to burn you at the stake," a person in Wyoming wrote anonymously, after reading about Finley's museum, adding thoughtfully: "figuratively speaking."

"I've been told several times that this is taboo stuff and I have crossed the line," says Finley.

But hey, this is the '90s. We're supposed to be cool about these things. It's just another normal, natural process. Embarrassment and squeamishness are out, Menstrual Pride is in. No more hiding your tampons on the way to the ladies' room, or referring coyly to having a "friend visiting," or opting out of gym class because it's That Time of the Month. Now we're supposed to consider the environment and use cloth pads that you wash and reuse, first soaking them in a special jar and then pouring the waste water on your garden.

A sample of one of these jars is on display at the museum.

And yet it seems we have not as a society arrived at the point where the idea of a museum about menstruation fills us with delight. Finley knows this, although he was not prepared for the hostile reaction he got from his family.

Or, for entirely different reasons, from some women. There was the testy assessment in Sassy magazine ("stick to jock itch products, buddy") and the rebuff from the manufacturers of one line of new age napkins. They announced that they would not correspond with Finley "if you are a man." A couple of radio shock-jocks have suggested he is a pervert, he's had a few crank calls, and several friends expressed concern that opening the museum would bring on a police raid.

"I had to ask myself what this would do to my reputation," Finley says, sitting near the suspended mannequins. "But then I had to say, What reputation?' It's not like I'm the mayor of New Carrollton or anything."

He estimates that about 200 people have visited the museum so far, recently including a graduate student and her boyfriend who spent four hours doing research for her dissertation on advertising, four middle-aged women from Pennsylvania, one of whom is writing a book on euphemisms and synonyms for menstruation, and two video operators from New York.

The basement was cold on a recent spring morning. There are rose-colored synthetic curtains covering the sliding door to the outside, with matching tablecloths on two of the display tables. The floor is covered with beige industrial carpeting. There are two armchairs, and a resident cat named Mack C. Pad.

The collection now contains about 1,000 copies of advertisements, two dozen patent applications, old film strips that were used in girls' physical education classes, and dozens of tampons and pads that have been sent to Finley. These include several boxes of the infamous Rely tampons, the prime culprits in the deadly toxic shock cases of the 1970s. A psychoanalyst in Los Angeles -- a regular correspondent -- has sent a facts-of-life book from the 1950s and a rubber stamp of a motorcycle. (It's a somewhat obscure reference to the cycle concept.) A fan in the Midwest sent a box of 30 examples of menstrual underwear, and a variety of small businesses and pharmacies have donated examples of cures for PMS.

In real life, Finley works as a graphics designer for the federal government. When previous jobs required it, he held a security clearance. Before his assignment here in 1984, Finley spent 13 years as a designer for U.S. government publications in Germany, and there he noticed that magazine ads for pads and tampons overseas were much more "liberal" than in the United States. So he started adding them to his collection of antique and contemporary ads.

"I am every bit a product of my society," he says. "The subject was never mentioned when I was growing up. All I knew from the women I have been involved with was in terms of an inconvenience, or a barrier to sex."

He was raised an Army brat, moving frequently. He had an older brother and a younger one; no sisters. "Everyone always asks me that," he says. His younger brother died of muscular dystrophy at the age of 21; his mother died not long after. The experience was painful -- he thinks that it made him wary of marrying or having children.

He says his interest in menstruation is intellectual, and that he's filling a void -- as far as he knows there is no other Museum of Menstruation. "I have collected these things for years because I am curious about attitudes," he says. "The fact that it is taboo attracted me."

Ever since he majored in philosophy at Johns Hopkins, Finley has tried to find ways to combine his interests in teaching and art, and this may be it. "My contribution is nerve," Finley says. "I want this to be the world center for the study of menstruation, a place scholars can turn to for research."

Finley continues to seek information from anyone who wants to send it, and helps researchers at no cost. He publishes a newsletter, Catamenia (from the Greek katamenia, meaning "monthly"), and talks to any interviewer who calls. He has agreed to exhibit part of a work being created by an Iowa artist that involves stories about menstruation placed inside the little cardboard boxes airline sanitary napkins come in.

He has also been contacted by a college student who wants to serve as an unpaid intern this summer. "She has lots of ideas, like T-shirts," he said. "She also said that a lot of rock groups would love to be able to say they'd played the Museum of Menstruation."

So far there have been no exhibits about the controversy over whether tampons contain dioxin, or about premenstrual syndrome (PMS), but the ecologists' argument against disposables is currently given ample display.

Finley realizes that his preoccupation may limit the field of women he could go out with. "Like anyone else, I've had my highs and my lows with women," he says. "No woman I know would want to get involved with someone who had this interest -- would probably, in fact, be repelled by it. I realize that it's possible I may never have an intimate relationship with a woman again because of this. I am prepared to accept that."

In any case, he said, he can always be proud that he has actually done something that he wanted to do. It has been interesting so far, he said. "I had a pretty dull life before this." CAPTION: Harry Finley: "I had to ask myself what this would do to my reputation. But then I had to say, What reputation?' " CAPTION: Harry Finley in his Museum of Menstruation: "I've been told several times that this is taboo stuff and I have crossed the line."