AS AN executive who travels nearly three weeks out of four, Gail Brewer has experienced virtually all the classic horrors that plague the solo women traveler-restaurant seats near swinging kitchen doors, porters bypassing her in favor of men they assume will tip better, desk clerks who ignore her and address her male subordinate.

But Brewer's single most upsetting travel incident occurred the night she was confronted by a hotel staffer who mistook her for a prostitute.

"I was sitting in the hotel lounge wearing my business suit," recalls the 35-year-old Vienna, Va., native, describing a recent trip east from her Los Angeles home. "It was 11 o'clock, but I was still oriented to West Coast time, so I wasn't tired.

"I had wanted to get a good night's sleep so I'd be fresh for a marketing meeting the next day, and I'd hoped a glass of wine would make me sleepy. I'd checked in and gone to the lounge to relax after the long trip. After a few minutes, a hotel security guard came up and asked me if I was a registered hotel guest.

"I just stared at him, took a deep breath and said, 'Yes, I am.' The next day I spoke to the hotel manager."

These are the kinds of abuses Brewer has spent much of the last 18 months trying to correct. As director of specialty markets for Ramada Inns Inc., she has headed a special program designed to attract the fastest-growing segment of the U.S. hotel market--women. Employes of all 580 Ramada Inns are expected to complete an "awareness training seminar," which addresses concerns of traveling women and gives suggestions on overcoming typical slights.

"Our research showed that women don't want special services," Brewer notes. "They just want the same services, respect and courtesy accorded to male travelers."

Like Ramada, more and more members of the travel industry are designing special campaigns to attract the growing legions of traveling businesswomen--whose numbers are increasing at a rate three times faster than that for men. More than 30 percent of all domestic business travelers are women, up from just 1 percent in 1970, according to a study by the Cornell University School of Hotel Administration.

Women make up 19 percent of all international business travelers, notes a survey conducted by Opinion Research Corp. of Princeton, N.J. And about half of all domestic and international pleasure travelers are female.

Yet despite their growing numbers, "the majority of these traveling women feel they are still being discriminated against," says Francine Herman, an associate professor of hotel administration at Cornell, who cochaired a conference on women travelers. "We found that approximately 60 percent of the women we talked to used their hotel rooms to eat in, as contrasted to a very small number--10 to 15 percent--of men.

"The men used room service when they were having a meeting and didn't want to break to eat. But the women were using it to avoid the hassles that face single women travelers. Basically, they hid."

Food and beverage service account for most of the problems women report, Herman says. Although studies show that businesswomen are the best weekday restaurant tippers--leaving the server from 20 to 22 percent compared to 10 to 15 percent from men--"women still get poor service," she says, "because they've got the image of being bad tippers. Women also felt they were always subject to pickups by men, sometimes with the connivance of bar staff."

Some hotels now direct bartenders to ask a woman's permission before making her a drink or passing her a note offered by someone else in the lounge, Herman notes. "Also, some properties have put in the equivalent of captain's tables, where single travelers of either sex can choose to sit with other single travelers or sit alone.

"We're seeing more and more travel advertising geared to women. And rooms are being designed so they can be converted into studios where the bed disappears. Men have always felt perfectly okay inviting another man into their rooms, and this way women can feel comfortable with that, too."

Women traveling for pleasure experience some of the same problems as women traveling on business, says Californian Barbara Pletcher, executive director of the National Association for Professional Saleswomen and author of the women's travel guide "Travel Sense." "The less secure woman traveler may have even greater problems getting good service on a pleasure trip, because she's not likely to be wearing her no-nonsense navy suit. She may be more apt to let herself get pushed around if she's in jeans."

But women pleasure travelers are less likely to isolate themselves in lonely rooms, she says, "because fewer pleasure travelers go all by themselves. They're more likely to be with a friend or with family so they won't feel they have to hide and order room service. In business travel, the travel is often a necessary evil. But in pleasure travel it's part of the experience, so you want to be sociable."

If they are traveling solo, women often sign up for adventure travel, cruises and group tours, she says, "partly because they have the finances to swing it and partly because it assures they'll be part of a group whose interests they share. And I'm seeing more and more women going on wilderness survival trips, too, because they want to test themselves and see if they can do it."

But whether traveling for business or pleasure, safety generally heads the list of women's concerns, says Cornell's Herman. A typical problem is the tendency of desk clerks to announce a new guest's room number to the bellhop in a voice loud enough for the entire lobby to hear.

"It's a terrifying feeling to be alone in a hotel and know that some stranger knows what room you're in," says a California businesswoman. "On one trip, I'd been in my room about five minutes and the phone rang. A man's voice said, 'Hi, I was in the lobby when you checked in and wondered if you'd like to have a drink.' I wouldn't go back to that hotel again."

This kind of negative experience can hurt hotels, which thrive on repeat business and word-of-mouth recommendation, says Donna Saracco, editorial director of Solo, a 5,000-circulation newsletter for women travelers. "The industry is waking up to the enormous buying power of women travelers. In most major cities today there are several hotels and restaurants where women can go and feel comfortable. In our newsletter we recommend places where a women will get respect, not hassle."

Women traveling abroad often find their treatment varies with the country, Saracco says. "When traveling on business in China I found people extremely respectful and friendly. But you do need to learn the local customs. The one place I didn't receive a warm welcome in my hotel was in the bar. I discovered that women don't go into Chinese nightclubs alone because they're seen as competition for the hostesses."

Women traveling in Europe generally can expect "standards of behavior equivalent to what they'd find in the United States," writes Penelope Naylor in "The Woman's Guide to Business Travel." "But in some other places in the world, women doing business and traveling on their own are more than suspect. Without a husband or a father to protect them, they're considered, like Victorian-era actresses, little better than prostitutes. This is most often true in the more conservative countries of the Mediterranean (Spain, Portugal, southern Italy, Greece), all Arab countries and most Moslem countries, a good bit of the Orient and Latin America."

Her advice to women traveling abroad: Study up on local customs before you go. "In Saudi Arabia, for example, you should know before you go that women are expected to cover their arms and knees, and they should never smoke in public or in front of business associates unless the host lights up first." In deference to local attitudes, some international branches of U.S.-based hotels do not feature the "women travelers" promotions offered by their American counterparts, Saracco says. Domestically, these travel industry programs geared to attracting women travelers range from providing simple necessities--like shower caps and skirt hangers--to sponsoring major public relations campaigns. Among them:

* Westin Hotels (formerly Western International) launched an employe-training and public information campaign three years ago in which the company gave away nearly half a million booklets of tips for traveling women.

* American Express gives away a free "Business Woman's Travel Guide" and sends an executive to speak to interested groups about "Taking Your Business on the Road."

* Eastern Airlines offers a "Woman on the Go" seminar, featuring an airline representative presenting a program of hints for women travelers.

* Marriott supplies rooms with skirt hangers, shower caps, Vidal Sassoon shampoo and special soap and provides "a blow dryer for hair on request." Each room has two locks, plus a chain lock and one-way viewing hole.

* Four Seasons Houston has "mini-suite" rooms in which the bed is tucked in an alcove and the sitting area has "several pieces of furniture instead of the customary couch." Available on request: blow dryer, iron and board, plastic hangers, soap for hand-washables, heating pad, lint roller and scissors.

Although none of these companies can give exact figures on the amount of new business they have won as a result of their efforts, at least one private entrepreneur has cashed in on the traveling women boom.

"I couldn't find a briefcase or garment bag suited to a woman," says 33-year-old Susan B. Engel, who quit her job as a marketing manager for a medical instrument company two years ago to start her own New York-based firm designing products for women executives.

After the first year, Susan B. Exclusives netted about $150,000 on sales of the attache' case alone, and Engel now markets everything from a combination smoke alarm/burglar alarm/flashlight to an "extremely classy raincoat" that folds into a tiny pouch.

Sometimes, however, well-meaning hotels miss the mark in their efforts to cater to businesswomen.

"On a recent business trip a male colleague and I arrived together at a luxurious new hotel," recalls Carolyn Eldred, a research psychologist with Washington's Aurora Associates Inc. "My room had an attractive color scheme--gray, green and rose--and there was an arrangement of dried flowers and a copy of Cosmopolitan.

"When my colleague phoned a few minutes later, I couldn't resist asking him what color his carpet was. He replied 'dark green.' He didn't have any flowers, and instead of Cosmo he got the Wall Street Journal."

As much as Eldred enjoyed the pretty carpet and flowers, she notes, "I'd have traded them in a minute for the Journal, which I read at home every day."