Some young women keep it in their head, others in a drawer of their bedside table. One even preserves it on a spreadsheet in her laptop.

We're talking about "the number," that sum of sex partners that college women either have had or hope to goodness they can avoid reaching. In the highly sexualized atmosphere of campus, a number gives them something to compare and dish about with their close girlfriends.

Jennifer Broussard, who graduated from the University of Pennsylvania a year ago, used to tally up her companions on a sheet in her organizer, attaching dates and footnotes. She'd dial up a girlfriend to ask things like, "What counts? What doesn't? I'm about to pass my benchmark. Is this guy worth it?"

Keeping score is not new, of course. Think belt notches of yesteryear or a general estimate, privately held. As some sexually transmitted infections increase among the young, keeping a number and names could even be the responsible thing to do.

But chatting about -- and even recording -- each incident in detail?

"We always talked about the number in high school -- in secret," says Broussard, who works in Manhattan for a consumer product licensing agency. "Now more and more of us are admitting that it is not something to be ashamed of. We're clearly more open about it with each other."

These women analyze their numbers as if they were comparison shopping for the right size and color of shoes. They tell each other that sex is separate from love. And few adults tell them any different. Sex education teachers lecture on body parts and disease, and we know that parents would rather throw themselves in front of a truck than talk in depth about sex and romance.

"You're seeing a group of girls whose mothers raised them to accept that they have sexual needs and desires [and] that they need to use protection," says Anna Schleelein, a rising senior at Boston College and the school newspaper's former sex columnist. "Beyond that, [mothers said,] 'What you do is your business.' "

Psychology professor Elizabeth Paul has studied students' sexual relationships at the College of New Jersey, a state school near Trenton, and has been struck by the complexity of their nightly, weekend and overall tallies. "They keep track of different experiences. This week it might be a lip ring 'to see what that's like.' Their marks might include what was fun, what was bad."

Such micro-analyzing can seem, well, clinical. Where, on a spreadsheet, is there room for passion one can't explain? Aren't the details of intimacy sweetest when confined to the couple?

That thinking may be so last century for young women who came of age with movies like "American Pie" and TV shows like "Dawson's Creek" and "Sex and the City." Why should numbering sex partners be any different from tracking the hours you sleep, the calories you consume, or the miles you jog every day?

Kristin Thorne, who graduated this year from Georgetown University, attended a Catholic high school where, she says, "girls typed up lists showing how many guys they hooked up with." ("Hooked up" is a deliberately vague term coined by this generation to mean anything from serious kissing to intercourse.)

Once they arrived at college, two friends told her they planned not to have sex with more than 10 guys, but if they did, number 11 would become their husbands. "I think they were hoping to settle down," Thorne said.

Then number 11 came along. They called Thorne and "laughed at themselves. They've now moved beyond that number and are still searching."

The search for the one man who will lead them to forsake all others is a process that will take longer for many young women than it did for their mothers. With college, graduate school, study abroad, or job changes ahead of them, "it doesn't make sense to start a serious relationship in college," says Susan Harrison, a senior at Brown University who keeps a mental list of her partners.

Anticipating these years on their own, the women begin indulging in short-term flings while worrying about bumping their number up beyond an acceptable limit.

What? Worry? One thing hasn't changed. The more partners a woman is known to have, the more likely she is to become the object of a whisper campaign by others who have less experience.

"It's easier to say, 'So-and-so's a slut' than to say, 'I'm not at that place yet,' " explains sophomore Veronica Searles, a confidante to classmates at Brown. Searles says a young woman will also worry, as previous generations did, "how men will view her down the road."

Push these women and you discover that some of them act a lot like male "players." One of professor Paul's freshmen said she uses her number to compete with friends back home. Another said she views each encounter as a conquest.

Does sexual bookkeeping represent progress? If a young woman is using numbers and conversations about numbers to understand more about herself, relationships and what constitutes going too far, "maybe that isn't all bad," Paul says. But if a girl tallies up her encounters because guys do, or her girlfriends do, or because her self-confidence needs a boost, she should think again.

Brown student Searles worries, too, about comparisons-by-number. Some of her friends are virgins, she says, and hold themselves up against the more experienced students, asking "How far behind am I?"

"They see themselves as odd although they're not," Searles says. "They're almost ready to jump the gun because they're behind."

The National Campaign to Prevent Teen Pregnancy, an educational organization, estimates that a woman who has sex for the first time her freshman year of college will end up with four more partners before graduation. But that's the average; it's not unusual for young women to talk about an outside limit of "two hands" or "getting to double digits."

By the time the third or fourth year of college rolls around, a little creative accounting may be required.

Julia Baugher, who graduated this month from Georgetown, wrote about numbers in her sex column for the student newspaper. "If x = Number [that women] say they've slept with," she wrote, "then the Actual Number is x + Number she wishes she hadn't slept with."

"I used to be really [picky] about my number," says Baugher, who keeps a running total on a computerized spreadsheet with side comments such as "weird teeth" and "future med student."

"I said everything counted," she continues. "I was approaching double digits and I didn't like it, but I didn't think there was anything I could do about it."

Then she came across the irreverent paperback "The Catholic Girl's Guide to Sex," which lists all the reasons a girl can use to knock a guy off the list: She was drunk, or on vacation. It was an accident, or he was an ex.

Yes, boyfriends can be recycled and not boost the total, Danya Resnick, a rising junior at the University of Virginia, asserts. Resnick has a close friend who told her she was returning to Washington for a weekend and planned to have sex with an old boyfriend. "It won't increase the number because I already slept with him," the friend told Resnick, who adds, "I've heard many stories like that. It makes more sense than it used to."

Four female freshmen at Georgetown University were sunning themselves on Healy Lawn on a recent afternoon and talking about hooking up -- or "choching" (pronounced cho-ching) as they call it -- for a reason they can't explain. Choching, as they've experienced it, hasn't included intercourse yet. But then they were joined by another, more experienced freshman who just returned from spring break.

She and her friends held a contest while sharing a hotel room in Cancun. After each night out, they gave themselves one to four points for certain sexual behaviors, with four signifying going all the way. They recorded the points on a poster board and agreed that the student with the most points would win.

In that one week, she acquired 19 points. And lost the competition.

The winner, she said, scored 20 points -- "seven in one night."

Penn graduate Broussard, four years older than these freshmen, predicts that eventually the quantity of the young women's relationships will come to matter less than the quality. Still, she doesn't play down the significance of keeping a number. "If you don't put it down, you could be in denial, forgetting everyone you're with. Who knows what number you would reach?"

She recently discussed this with her boyfriend.

"He got all nervous and said, 'I know that you're free sexually and that's great.' . . .

"I explained that it's not that I should be able to do anything but that I'm comfortable with my sexual decisions," she says. "I don't want to forget the names on my list, whether they're good or bad. I like to remember them, learn from them."

One thing the list has taught her, she says, is to take time with a relationship, allowing a man's feelings for her to emerge -- either before or after sex -- rather than expecting them to be there from the beginning.

"Sex isn't what determines if a relationship works or not," she says.

Julia Baugher, left, and Kristin Thorne, both recent graduates from Georgetown, have had discussions with friends about "the number." "I don't want to forget the names on my list, whether they're good or bad," says Jennifer Broussard. "I like to remember them, learn from them."