Bosses who demand or expect sex from secretaries or other subordinates are unable to tolerate frustration; insecure about their masculinity and self-worth; often, shy, or trying to get back at their mothers; psychiatrists say.

And the women -- who may comply out of fear, file complaints of sexual harassment or quietly switch departments or jobs -- are sometimes partially at fault for sending out mixed signals, overreacting or misinterpreting casual remarks, they say.

Sexual harassment is used to cover a wide variety of behavior, ranging from being subjected to dirty jokes in the office to being told by your boss he wants to talk with you about your work -- in bed.

But in the strictest sense, it means having to be sexual as a prerequisite for a job or promotion or good grade; and reports of it are increasing despite -- or perhaps because of -- the women's movement.

"We are seeing an increasing number of complaints filed alleging sexual harassment, I think, because of women's increased awareness that this is a prohibited act," said Carol Schiller, assistant chief of California's division of fair employment practices here.

Sex discrimination now accounts for nearly half the complaints filed with the Equal Employment Opportunity Commission, according to Daisy Voight, a spokesman in Washington. Of the more than 30,000 complaints filed in 1978, however, fewer than 1,300 fell into the category of "intimidations and reprisals," where most sexual harassment complaints fit.

"We don't separate it out," Voight said. "It's discrimination, whether the guy says women are incapable of certain jobs or says outright, "Let's get it on.'"

The experts say they cannot say with certainty whether more reports of sexual harassment mean that the social climate has changed; that women are growing more hostile toward men; that men are clinging desperately to their office bastions of power, that women caught between old cultural patterns and new-found freedom are behaving inconsistently, or that men are showing less respect for women and social conventions in general.

Dr. Mel Mandel, director of the Los Angeles Psychoanalytic Institute, suggests that perhaps the incidence is the same but the complaints have risen because of a social climate that elicits minority complaints. Or that bosses' sexual demands or expectations are truly up because a number of men equate a woman's freedom with her approchability.

"They develop a fantasy that women are now more free and receptive, that they don't have to be coy, that they can be more open and direct," Mandel said.

Whenever men and women are thrown together -- socially or in the workplace; he says, seething sexual fantasies are never far away. But such thoughts are unconscious or fleeting for most, and both individuals get on with their jobs and careers.

But when one person uses his power to force another into unwanted sexual relations, that becomes a kind of rape, albeit a heretofore socially sanctioned rape that uses psyhological or economic rather than physical force.

Asked what is erotic about having sex with a woman because she needs the job or promotion her boss controls rather than because he is attractive, Mandel explained, "There is something about the exercise of power that is an eroticizing and exciting prospect for a number of women in subjugation."

It's the master-slave fantasy played out, and reveals what Mandel calls the "sadistic underpinnings" of sexual response.

Dr. Joseph Golden, director of UCLA's human sexuality program, agrees. Sleeping with your secretary, paying a prostitute using the casting couch ploy and rape itself all involve the use of power, he said.

"And anybody who has to coerce another into sexual relations or seeks to have sex without developing a relationship is either sexually unhappy in his present situation or trying to establish something that is not primarily sexual -- dominance, power, attractiveness, youth, etc." Golden said. "In fact, it may have nothing to do with sex."

Mandel describes such men as "insensitive; inferior and inadequate" and trying to compensate via power and money and sex, Don Juans who seek to control women and compete with other men. They may view all women as objects to be depreciated and controlled or divide females into "whores and mother" -- idealizing their wives and mothers and seeing women in the workplace as theirs for the asking.

Another Los Angeles psychiatrist, Dr. Irwin Ruben, divides amorous bosses into four general categories: frustrated, macho, shy and mother-loving: b

The frustrated boss is used to getting what he wants and has never learned how to tolerate the frustration of his wishes, sexual or other.

The macho man is still an adolescent who needs sex to prove he is a man and able to be in charge. His masculine self-esteem is low.

The shy employer sees power as his only way to getting sex and is unlikely to seek -- or get -- gratification, sexual or otherwise, outside the job. He does not know how to relate to another human being except through holding power.

The mother-hater seeks, through other women, psychological revenge on a mother he perceives as withholding and cold. He wants to dominate because he was controlled as a child, and goes through life stepping on women.

And as for the women, they often send out conflicting signals; they seek success with their brains, but drag with them to the office a lifetime of learned behavior labeled "feminine" and "flirtatious."

From earliest childhood, people react to little girls in frilly dresses with "She's so cute." Ruben explained that some women may fear they cannot make it without appearance and consequently may dress and act provocatively.

"Many women are seductive because they've been taught to be seductive," Golden said. "And it's not very clear -- to yourself or to the other person -- when you're being seductive just how far you intent to go. It's easy to read more into the situation, when a person is warm, responsive and gives you attention when you're feeling needy, than he or she intended."

A man may think he sees approachability in a woman via a look in the eye and a flirtatiousness she's not even aware of, Mandel said.