You may wonder why we brought you together ...

One of television's most durable sitcoms, "The Odd Couple," depicted hilarious conflicts between a neatness freak and a sloppy sports fanatic living together in a small apartment.

But for 1.7 million college freshmen this fall, the prospect of getting saddled with the wrong roommate is no joke. Just ask Kelsie Costa.

"I had a roommate who thought she had a single room," says Ms. Costa, a freshman last year at the University of Colorado at Boulder. "She had her boyfriend over night and day. When I was studying, she would watch TV. If I was watching, and she wanted to study, she would just turn it off."

After a number of debacles, Costa made a decision that colleges dread: She transferred.

To freshmen encountering the demands of college-level study, an inconsiderate roommate can be a serious distraction that harms grades, confidence, and commitment to the school. For all those reasons, bad roommate situations can be costly to colleges as well - prompting some to exercise greater care in creating matches that have to survive the vicissitudes of freshman year.

"It can make or break a college experience," says Joan Schmidt, president of the Association of College and University Housing Officers International. "It can be the last excuse before they say: 'That's it, I'm out of here.' "

Beginning about 1980, many colleges tried to improve retention rates by identifying and pairing like-minded freshmen using psychological tests. Most saw little improvement and returned to a random approach, Ms. Schmidt says.

Today, schools typically begin by sorting freshmen into a few categories before the random matching. Most schools do avoid placing smokers and nonsmokers in the same room. They also may ask about a few preferences: for instance, whether a student gets up early or studies late.

But a few schools are still experimenting with ways to get the freshman roommate match just right.

At the University of Texas at Austin, housing officials have devised a Web-based system that asks students about smoking, sleeping, exercise and study habits, music, frequency of visitors, interest in fraternities, and computer use. And the list is growing.

"We kept asking how we might make it possible for students to ask each other these questions," says Sheila Ochner, associate director for housing and food. "We wanted to get ourselves out of the equation."

At UT-Austin, 2,800 students filled out online profiles to help pick roommates for the fall. Students can comment on the importance of various issues: "I would prefer a roommate who listens to music while studying (Yes, No, Sometimes)." Or, perhaps: "I would prefer a roommate with this level of cleanliness: Very Neat."

The website compiles students' answers into a checklist profile that also includes name, e-mail address, and phone number. Students then sift through the database, making their matches according to their own criteria.

It's not the ultimate answer to the roommate dilemma. Some still are matched randomly. And some self-matched roommates still request changes. But Ms. Ochner hopes the system - in place for two years and still being refined - will yield better results than a random approach.

Taking a sharply different approach is Davidson College in Davidson, N.C., where freshmen roommates are matched painstakingly by hand with attention to so many details that one official describes it as a complex "Rube Goldberg" system.

Davidson officials spend several weeks each June matching just 475 freshmen. First, they take results of a Myers-Briggs personality type test (extrovert, introvert, etc.) and put complementary types together. Then habits and preferences of entering freshmen filled out on cards are weighed. (Early birds and night owls are grouped, for instance.) Finally, admissions files are reviewed to match economic, academic, and family backgrounds.

"It's both science and art," says Leslie Marsicano, Davidson's director of residence life. "Some institutions have tried to rely only on the science side. They send you a form, you fill it out, they scan it. If you match 6 of 10 variables, you're roommates. We deal with the art side, too."

The "art" of Davidson's system means a freshman who is an only child with a single parent would probably not be matched with the youngest of 10 children living at home with two parents. Likewise, a vegan would not be paired with the son of a cattle rancher, Marsicano says.

But critics say pairing roommates who are alike misses the point - that college is all about having a roommate different from you so you can learn more from each other. Marsicano agrees - up to a point.

"We would put them on the same hall," she says. "We want ... a diverse neighborhood. But in the room, we're looking for compatibility. We think it's a lot to ask of the vegan and the cattle rancher to live together in the same small room."

Davidson's results speak for themselves, she says: a retention rate from freshman to sophomore year of 97 percent; a 90 percent graduation rate; and about 40 percent of sophomores rooming again with freshman-year roommates.

"We've been pretty compatible, living together for three years now," says Shanna Cockman, a Davidson junior majoring in psychology.

Roberta, her volleyball-playing roommate, is "kind of the shyer of the two of us," Ms. Cockman says. "I'm kind of the other way. She's really like a sister to me now more than a roommate."

Davidson's system might seem unwieldy at Michigan State University in East Lansing. Of 15,500 undergraduates living on campus, nearly 7,000 are freshmen.

Michigan screens academic and living-space priorities, then smoking and a few other categories. Names then go into a lottery system. But some parents insist their child be allowed to room with old friends.

"What we do find is that those are usually the relationships that break up first," says Angela Brown, director of university housing. "It's almost as if they are too familiar with each other. Students tend to be more tolerant of someone they don't know than someone they do."

Arash Mahajerin, a junior at Michigan, may be an exception. He had known his first roommate since third grade. It was a good year. "I figured things would be fine as long as we were both honest and up front with each other," he says.

His tips: "Be neat. Don't leave clothes lying around, CDs, books - and really respect when it's time for the other person to study," he says. "We're here for an education, after all."