At Ellen Seeherman's wedding last June, an unusual "maid of honor" proceeded her down the aisle -- fellow attorney Paul Glickman.

"Some of the guests seemed a little surprised," admits Glickman, who became friendly with Seeherman in law school and threw her a "bachelor party" the week before the wedding.

"But to us the whole thing made perfect sense. After all, I'm her closest friend."

Historically, the lives of men and women have intersected rarely -- mostly at mealtime and at bedtime. But today, with increasing numbers of women working alongside men, the sexes have unprecedented opportunities to associate.

Add to this frequency of contact a new focus on equality between the genders, and the result, says Washington psychiatrist E. James Lieberman, is a "broad-based social change in the ways men and women are relating.

"Men and women are learning to relate to each other as people primarily, not as sex objects. In the past it may have been considered strange for a man and women to be close friends, yet not be involved sexually. Now it's becoming more accepted."

The French call this special kind of relationship "aimite en rose," or loving friendship. "It is something more than friendship and less than love," says singer and composer Charles Aznavour, whose famous "amie en rose" was the late chanteuse Edith Piaf. "It is something very rare, very exquisite."

In English, a relationship between a man and woman that is spiritual or intellectual, without sexual activity, is called platonic -- after Plato's ideal of non-sexual love.

"Platonic friendships -- among heterosexual men and women -- appear to be growing," says Washington freelance writer Barbara Mathias, who is compiling a book on the subject. "But they are rarely talked about, because they are possibly the most difficult kind of relationship to maintain.

"We have no societal norms for platonic friends, so people tend to feel awkward and view the relationship with suspicion . . . Is one gay? Are they having an affair? And there's bound to be, at some point, a physical attraction that can be very difficult to deal with."

Sociological research affirms the difficulty of male-female friendships. Platonic relationships are impossible, concluded more than one third of the male respondents and 15 percent of the females interviewed by psychologist Joel D. Block for his book, Friendship.

Block surveyed more than 2,000 people, who comprised a representative sampling of middle-class America. Just 18 percent reported having close friends of the opposite sex. Those who felt male-female friendships were impossible cited complex social and biological factors, such as "men and women can never be equals" and "the sex drive is too strong to ignore."

In a 1979 Psychology Today survey on friendship, nearly three-fourths of the respondents agreed that "friendships with someone of the opposite sex are different from same-sex friendships." Major reasons were that "sexual tensions complicate the relationship," "members of the opposite sex have less in common" and "society does not encourage such friendships."

Why are platonic friendships so complex? In his "Little Essays," George Santayana laid out the obstacles this way:

"Friends are generally of the same sex, for when men and women agree, it is only in their conclusions; their reasons are always different . . . Friendship with a woman is therefore apt to be more or less than friendship; less, because there is no intellectual parity; more, because (even when the relation remains wholly dispassionate, as in respect to old ladies) there is something mysterious and oracular about a woman's mind which inspires a certain instinctive deference and puts it out of the question to judge what she says by male standards."

But it is for precisely this reason -- the sublime differences between men and women -- that some people seek out friends of the opposite sex.

"Men and women usually have some important different life experiences," says Chicago psychiatrist Anne Seiden. "By sharing these different perspectives they can enrich one another's lives.

"Just as it's a wonderful thing for a white person to have a close friend who is black, and vice versa, it's great for a woman and man to be close friends. They can learn things about the other's life experience they'd never discover otherwise."

"I think my marriage is enriched by my friendships with women," says California psychotherapist Alan Loy McGinnis, author of The Friendship Factor. "My women friends can help me understand my wife in a way my men friends can't."

"My platonic friend is like the brother I never had," says a Silver Spring woman who has remained friendly with a man she dated in high school. "I can talk openly with him about any relationship problems, and he provides a male perspective on the situation that's particularly helpful.

"We have lunch about once a month and talk on the phone a lot. He and my husband get along well, and we've become friendly with his girlfriend, so the four of us get together occasionally. If I'm in trouble, I know I could call him any time of the day or night, and he'd come through."

This kind of male-female friendship is rare, writes Margaret Adams in Single Blessedness, because of "the subtle, but persistent devaluation of the platonic, as opposed to the erotic, basis for a heterosexual relationship."

"Friendship, in general, is undervalued by our society," says Boston writer Karen Lindsey, author of Friends as Family. "Can you imagine someone saying we're 'just' lovers, the same way people say we're 'just' friends?"

Plato, however, viewed non-sexual friendship as more valuable than erotically-based friendship, says Gabrielle Brown, author of The New Celibacy. "Sexual fulfillment was, for Plato, the releasing of individual tension, rather than an actual merging," she says. "He felt you couldn't achieve a full union with another until you were unattached from sexuality. Only when you got past sex could you really unite with the other person.

"In a sense, then, platonic friendships require more work, and are even more romantic. It's easy to have sex with someone. It's not so easy to transcend sexual feelings and channel that energy towards striving for something bigger than both of you."

For these reasons, says University of South Carolina psychology professor Keith Davis, it is particularly flattering to be chosen as a friend by a member of the opposite sex. "It's an interesting kind of validation of one's worth . . . You feel, 'Hey, that person really cares about me.' "

"Once the sexual stuff is out of the way," says Connecticut composer Randall Hoffman, "the pressure's off and you can get down to the real business of living."

Which may be why, as French biographer Andre' Maurois said, "The best friends are former lovers."

The biggest obstacle to platonic friendship is usually one or both friends' spouses, says Davis, who has done several studies on friendship. "Once people get married," he says, "they are less likely to have close friends of the opposite sex.

"They are concerned that their spouse will see that platonic relationship as a threat. Even if there's only a psychological intimacy, it can still be threatening to a spouse, probably because most people want to think of the marital relationship as the most intimate, closest relationship. A spouse may think, 'Why does my mate need another friend of the opposite sex?' and may start to question the marriage."

Considering a spouse one's "best and only friend," says psychotherapist McGinnis, "is downright dangerous. No one person can fulfill all your needs. But it is important to consider your spouse's fears and feelings about your friendships with members of the opposite sex."

Platonic friendships are not asexual, McGinnis admits. "There's sex in the air any time a man and woman are together. I had lunch with an 85-year-old lady, who is something of a flirt, and there's no question that sex was in the air. That's what makes the world go 'round."

But what characterizes platonic friends, he says, "is not that there isn't sexual attraction, but that they chose not to act on it. Setting limits is critical for platonic friends. I see so many people get sucked into sexual relationships they did not intend to because they didn't set boundaries. And it proves distructive to their marriage."

It was this phenomenon of "unintentional" affairs that started writer Mathias compiling material on platonic friendships. "I was researching an article on adultery," she says, "and it seemed that many of the women who got involved in affairs were looking for friendship and companionship -- not sex. But our society has no real avenues for male-female friendships, so many of them had affairs."

By running ads in several national magazines, Mathias has contacted nearly 100 pairs of platonic friends around the country and has run a workshop on the topic. "People feel very strongly about platonic friendships," she says. "They're either very enthusiastic about them, or they're adamant that they can't work."

One reason male-female friendships inspire such passion, says psychologist Block, is that "in truth, most of us are ambivalent about our sexuality with opposite-sex friends and do not know how to resolve the dilemma comfortably. Some men and women resolve the dilemma neatly -- they do not choose each other as friends. Others are so indiscriminately sexual that they shatter any hope of closeness with a single individual."

Often, it's only circumstances that keep platonic friends from acting on a sexual attraction, says psychiatrist Lieberman. "Under other conditions -- if they weren't married, or if there was no age or religious difference or whatever -- something could happen. If they decide not to be sexual, they have to continually be watchful to keep it that way."

Controlling sexual action is easier for women than for men, claims surgeon James Neely, author of Gender: The Myth of Equality. "Every 48 hours her sperm count doesn't complain. The male of the species lives his sexual tension at a higher level."

Our cultural tradition also permits -- and encourages -- women to say "no" to sexual desires or advances, while not allowing men the same privilege. "The assumption that many men hold," says Block, "that a real man will 'score' whenever possible, places undue strain on friendship."

Women may also have less difficulty with platonic friendships, says San Francisco psychologist Lawrence Weiss, "because women are more comfortable with friendships, period. Women are much more able to share their feelings and become intimate."

From his long-term study of "interpersonal networks," Weiss concludes: "In general, women are more skilled at interpersonal matters -- empathy, listening. Men feel they have to be strong and have trouble confessing inner dilemmas, where women can let down their hair. So it's not surprising that both men and women prefer confiding in women."

Younger people are more likely than older people to have opposite-sex friends, he says, because "older people grew up in a time when such things were taboo." And single people are more likely to have platonic friends than married people. "There seemed to be sort of an unwritten rule among newlyweds," he says, "that they could maintain opposite sex friends they already had, but didn't dare establish new ones after marriage."

A common way people satisfy needs for platonic friendships without threatening their mate, says Weiss, "is for a couple to make friends with another couple. That provides an element of safety, while allowing friendship with a member of the opposite sex."

The trouble with platonic friendships is not biological, says Block, but societal. "In our culture," he says, "we have overemphasized the separation of the sexes and the pursuit of sexual fulfillment. Men and women together in a bond of friendship are suspect: Is one homosexual? Are they having an affair? Is he impotent?

"But in other societies, friendships are instituted between men and women and last a lifetime. This demonstrates that platonic friendships are not only possible but can even thrive if the practice is culturally encouraged."

However, he cautions, "Ideal solutions exist only in an ideal world. In the real world, the best we can do is seek options that fit our individual natures and do not violate our cherished values."