They knew he had to go when they found his list of their girlfriends - complete with a physical descriptions and phone numbers.

Lauren and Joanne, two Capitol hill receptionists in their mid-20s, had just entered the increasingly common Washington world of co-ed group housing. They got out as fast as they could.

"The trouble wasn't that I had a male roommate," recalls Lauren. "It was the fact he was a nurd. He was always saying things like, 'Why aren't you doing my laundry?" or 'Women should cook for men.'

"We had the lease, so we finally told him we were planning to move, and that he'd have to find another place. We stayed, of course, and a girlfriend moved in after he left."

Although complaints - about everything from lousy bathtub-scrubbing to noisy poker parties - may abound, real horror stories about group living are few and while the term "group living" inspires visions of '60s communes - with pot-smoking on a shared mattress - today's group houses often consist of breifcase-toting professionals.

"Washington is so transient it's been happening here a long time. Because of the economy, and because most women in their 20s aren't getting married, the ages of people in group houses has been going up and up," says Betsy Neal of Roommates Preferred, a roommate-matching service.

Neal estimates 90 percent of her clients are looking for someone to join a house of four to five people, instead of looking for a two-person arrangement.

"The high divorce rate has added to co-ed housing. I've had people say that despite the fact a marriage didn't work out, they're used to living with someone of the opposite sex. So a group of professionals who are making good salaries get together and rent a nice place," Neal said.

"Ninety-nine percent of the people I interview want some communication with housemates, if even on an informal basis," says Neal. In the past several years she has placed single parents with children in group settings. She also has on file recent divorcees in their 40s or 50s. "Lots of these people have seen their kids do it, so they go into group housing."

Every housing has its own personality but they seem to fall generally into three categories: the committed, the casual, and the "I-can't-afford-to-live-anywhere-else."

"I really think we are an outpost of the '60s. It's going back to a community feeling. I'm constantly having to share, and be considerate. It's good for me," says Kathy Durso-Hughes, 29, who works at the Environmental Action Foundation and shares a large house in Takoma Park with two other women and three men.

"I reject the young married couple syndrome," says Durso-Hughes, who is separated. "I spent six of the seven years I was married living that way. If I got back together with my husband we would live in a group."

Four of Kathy's roommates work in public-interest groups.The others, Roni Falk, 24, is a physical therapist and John Harper, 25, is a lawyer with the IRS.

Their Takoma Park household exemplifies total commitment to group living. The six eat dinner together every night; cooking and clean-up is done on a rotating basis.

The furniture was bought cooperatively with funds contributed to the household checking account. An accounting system was worked out by Harper to make sure expenses for meals are shared equitably.

"The system has worked really well, but John's the only one who understands it," says housemate Mike Mawby, 25, a staffer at the public interest group SANE. The $600 monthly rent is divided on a graduated scale according to bedroom size, a practice many group houses employ.

The issue of what to do about an in-house romance is one many groups have to deal with eventually, though most groups start off with strictly platonic intentions.

"There is a trend toward the ability to make arrangements that give a sense of intimacy, but that do not require a commitment in any long-range way," says Richard Stephens, a sociologist at George Washington University. "You can plan a life with a number of intimate relationships, as opposed to the traditional model of one person being all things. This leaves a lot of room to be single and have at the same time a satisfying set of relationships that give emotional support."

"I'm the only person here who's never dated a housemate," says Dave, 29, a librarian who shares a Capitol Hill home with five others. (For reasons of privacy, this group and one other interviewed preferred not using their last names.)

The three men and three women ranging in age from mid-20s and early 30s, work at congressional offices or executive agencies and have been living together a year.

"I pay less than $100 a month in rent," says Darryl, 25, a budget analyst with the National Endowment for the Arts. "If you're just moving to a new city, it's a great way to meet people. It's a lot better than plodding around singles bars."

Except for community supplies of milk and mayonnaise, each housemate is responsible for obtaining and preparing his or her own meals. And it's not unheard of for one housemate to have a dinner party to which the others are not invited.

Another example of a group house with definite, if casual, commitments was organized in Cleveland Park by a divorced man and his two sons.

"The bottom line was economic," says Don, 36, who works at the Library of Congress. "As long as the two boys were living with me, I knew I couldn't be happy in a two-bedroom high-rise. I also think kids function better in a family. I think everyone functions better in a family."

In a great leap of faith, he rented a six-bedroom $950-a-month house and began advertising in the newspaper and on bulletin boards. For a lot of potential housemates, two boys age 11 and 15 had as much appeal as "a pet alligator," but Don finally assembled a household of five adults ranging in age from a 20-year-old National Zoo woman intern to a 40-year-old male architect.

"It's been a good support for me," says Denise, 28, a graduate student. "When I think of alternative life styles, I appreciate how much I get from living with many people. I haven't lived with children since I left home. I forgot how much a 15-year-old can contribute."

John Forbes, 36, a State Department foreign service officer, established a group house two years ago after he and his wife were separated.

"I didn't want to move into a small efficiency where I would be climbing the walls," he says. Sharing a large renovated house at Logan Circle are two men, a lawyer and a construction supervisor in their early 30s and a woman in her 40s.

They keep privacy to a maximum and group contact to a minimum. But, as Forbes said, group living gives him the choice of coming home and having someone to talk with "or going off to read a book."

Though they are responsible for picking up after themselves, the group hires a maid to clean the house. Meals are paid for and prepared individually.

While Forbes said people respect each other's privacy, there's no way to fool oneself into thinking the house is one's own.

"For a while I was sharing a bathroom with a woman who lived here briefly. It was always filled with frilly things and she had more bottles in there than most people have in a lifetime."

No matter how agreeable group living is for some devotees, most concede that it is not forever.

One well-functioning group house near Dupont Circle has had a fairly high attrition rate due to matrimony. They've softened the loss by making the ceremony a group celebration. One woman housemate, an Episcopal priest, officiates at all weddings. CAPTION: Picture, Takoma Park housemates John Harper, Mike Mawby and Paul D'Ari, from left, standing, and seated, Roni Falk, Noella Driscoll and Kathy Durso-Hughes; by Joel Richardson-The Washington Post.