Then, slowly, some come around. A few even become imbued with a missionary zeal to spread the word.



"I love it," said Rachel Jenkins-Stevens, 25. "I bought one in 1998, and I've only used about five tampons since."

Menstrual cups - soft, flexible cups inserted to catch menses flows - were first patented in this country in the 1930's, but never became popular. They are still hardly the rage, but use of them is growing, especially at women's colleges and through alternative health Web sites.

Safety questions have been raised, but so far the cups have not been linked to toxic shock syndrome or any other medical problem.

Two brands are sold in the United States: the Keeper, released in 1987, which is made of latex rubber and is reusable, and Instead, released in 1997, which is made of soft polyethylene and is disposable.

Some women choose them because they fear that tampons raise the risk of toxic shock or that the fibers of bleaches in them may cause harm. Some like the savings: a $35 Keeper is supposed to last a decade, while a 10-year supply of tampons may cost about $650. (Instead is pricier: a 10-year supply would cost about $400.)

Some like the convenience, an end to purses full of bent applicators and crumpled pads. Some appreciate that many women can wear them without leakage for up to 12 hours, even swimming, exercising or sleeping. Some like the fact that Instead can be worn during sex.

Some feel better about not adding tampons to landfills. (Scientists in Biosphere 2 wore the Keeper.) Some celebrate "moon flows" and want a closer connection to their own menses as a symbol of womanhood. And some mistrust the conglomerates that make tampons and want something "sort of antiestablishment," said Ms. Jenkins-Stevens.

As Harry Finley, the founder of the online Museum of Menstruation and Women's Health, which covers the history and culture of menses, put it: "It'll never become mainstream in America. It involves too much contact with the body, and I think most women are squeamish about that."

Even the president of Instead Inc. agreed: "This product isn't for everybody."

The cups for the two brands, one ounce each, are folded and inserted into the vagina with the fingers.

The Keeper is longer, sits lower and has a stem on the bottom that makes it relatively easy to pull out, empty, rinse and replace. Instead sits just under the cervix and is somewhat harder to hook a finger under. It is removed every 12 hours and thrown away.

Mary F. Frost, the president of Instead, says her company sells 12 million to 15 million cups a year, enough for about 150,000 women. Most are sold in pharmacy chains.

The president of Keeper Inc., Lou Crawford, refused to give exact sales figures, but she said the business sold "tens of thousands per year."

Francine Chambers, who runs on of the largest Keeper distributorships at the Internet site www.keeper.com, said the cup "was finally catching on in the last three to four years" and estimated that perhaps 100,000 women used them. Brenda Mallory, president of GladRags, a washable pads company that also sells Keepers, said her sales, mostly wholesale to health-food stores, had tripled in the last three years to 2,424.

Mr. Finley, whose museum is in his Washington area house but can be seen only online, has not data, he said, but many letters from happy cup users and a few dissatisfied ones are posted on his semi-humorous, semi-scientific Web site, www.mum.org.

The first cup in this country was patented in 1937 by Leona W. Chalmers, an actress, who in her promotional pamphlets referred to earlier European designs. Wartime rubber shortages put her company out of business, but she later teamed with a venture capitalist to market two successors, the Tassette and the disposable Tassaway. A quaintly discreet 1961 Times Square billboard for one displayed only a tulip and this description: "Not a tampon, not a napkin. Now, a better way."

The company collapsed, but 20 years later, the Keeper was developed by Ms. Crawford, who had owned a Tassette.

Dr. Armand P. Lione, an independent toxicologist in Washington, recently raised safety questions about menstrual cups, saying he thought they might increase the risk of toxic shock syndrome because they hold blood in the vagina. The syndrome is caused by toxins from staph or strep bacteria; an outbreak in the early 1980's that killed about 35 women was linked to superabsorbent tampons, prompting tampon makers to change the materials they used.

Dr. Lione argued that cups might also raise the risk of endometriosis, a condition in which cells of the uterine lining sloughed off at menses flow backward up the fallopian tubes, escape into the abdomen and adhere there.

He contacted the National Women's Health Network and the Endometriosis Association, but they declined to ask the Food and Drug Administration for safety reviews.

Amy Allina, the network's policy director, said she thought Dr. Lione's concerns were "plausible, but fairly hypothetical," but she said she did not find alarming patterns. The F.D.A. database of complaints contains one about the Keeper and 13 about Instead.

Mary Lou Ballweg, president of the Endometriosis Association, wrote that it was normal for women to have backward flow into their abdomens, but that was not the apparent cause of endometriosis.

The Keeper was never rigorously tested before the F.D.A. accepted it in 1987; rather, the agency ruled it "substantially equivalent" to the Tassette, which was on the market decades before the agency began to regulate medical devices.

Dr. Philip M. Tierno Jr., director of clinical microbiology and immunology at New York University Medical Center, whose research led to many changes in tampons, said he gave the Keeper a simple test. He dipped it in a broth of staphylococcus bacteria, incubated it in a warm, moist atmosphere and checked its surfaces. "Miniscule quantities" of bacteria adhered, he said. "I don't think it would be a significant problem."

Dr. Tierno never tested Instead, but said he would "be uncomfortable" with a cup worn so high up because it could create an environment like that of a cervical cap. Caps - small birth control diaphragms that fit closely over the cervical opening - are not supposed to be worn during menstruation, but when they are, he said, "they have given rise to episodes of toxic shock syndrome - although it's rare."

But Dr. Barbara B. North, the medical director for Instead, said its cup passed an "extensive" set of laboratory and human tests before the F.D.A. approved it. They included tests like Dr. Tierno's, tests on human skin cells and live rabbits for allergies and toxicity, and finally tests on 300 women in seven cities who wore it for three to nine months.

"We looked for any changes in the microbial flora - staph, the normal lactobacillus and other pathogens," she said. "There was nothing." Ms. Crawford said half of her Keeper sales came from women telling one another about the product.

Isadora Forman, a 21-year-old classics and religion major at Mount Holyoke College, said she was one of 11 students she knew who used it. She just helped buy one for a friend's 16-year-old sister. "Oh, she was totally excited," she said. "She's worried about dioxin and bleach in tampons."

(The F.D.A. says "unfounded rumors" are posted on the Internet, claiming that tampons contain dioxins from chlorine bleaches of asbestos added by manufacturers to encourage bleeding. The agency says that it has never found any asbestos, that tampon makers now use chlorine-free bleach and that dioxins are "at or below detectable limits" and present no health risk.)

Ms. Forman first heard of the cup, she said, from a boyfriend who learned of it in an environmental science class.

Then another woman gave her a lecture "about getting in touch with my moon flows, giving me this hippie stuff, and I thought 'oh...'"

"But, when I got back to school," she added, "it seemed like everybody else was using it."