"Mayflower Madam" Sydney Biddle Barrows, subtle as a scream, walked into the International Platform Association conference Wednesday morning with nothing more than a reputation. By the time she left that afternoon, she had become an ideal speaker.

The week-long IPA, which concludes today, has one chief purpose, according to the organization's executor Dan Moore. "It is the responsibility of the IPA," he said flatly, "to feed new people into the nation's lecture circuit as the old pros die off."

An ideal speaker for the late '80s, according to Moore, would be one whose presentation is riddled with humor, sincerity, pathos, topicality, a soupc on of controversy and, of course, a message. In Barrows, a Manhattan blue blood busted in 1984 for running a prostitution business, speaking engagement booking agents found it all.

The audience loved her. And hated her.

Dressed like a Sunday school teacher who spent her dowry on Calvin Klein, Barrows revealed that all of her "girls" came prepared for their $200-an-hour exploits. "They always carried bubble bath with them," she said. "Bubble bath is a big fantasy item for men." After this comment, two elderly women exited the Grand Hyatt auditorium. "She's trash," hissed one.

Barrows revealed that she did have high employment standards. "I wouldn't hire gum-chewing bimbos from Brooklyn with an eighth-grade education," she said. After this comment, every woman at a table for five rolled her eyes in disgust. "She's demeaning to all women," said one.

Barrows revealed that she insisted that her girls use conventional birth control methods. "I asked one girl what method of birth control she used, and she said 'astral-projection,' " Barrows said. "I said, 'Honey, that's not going to work.' " After this comment, everyone laughed.

And so on. And so on.

From Barrows and her prostitutes to Charles (Tremendous) Jones and his "keep plugging" inspirational sermon, to Malcolm Forbes and his business predictions for 1988, to playwright James Kirkwood and his behind-the-scenes look at "A Chorus Line," all 61 speakers at the IPA's 156th annual convention had a story to tell, a book to plug or a personal anecdote to explore.

And all in the name of the almighty greenback. The annual IPA conference, said Moore, can be a conduit to financial security. The system works like this:

The IPA invites speakers to the convention who it believes will ignite interest, support for the organization and a good time for the estimated 1,000 IPA members who are here just for that. Booking agents, almost all of whom prefer anonymity so speakers will not play to them, then evaluate the talent and book accordingly. ("It's fair to say," Barrows said after her speech, "that I won't be getting any church group bookings from this.")

The audience also has a say in the speakers' fates. Evaluation cards are passed out before each speech, and the results -- excellent, good, fair, poor -- are shown to agents. (The two women who walked out on Barrows said they would not massacre her with the evaluation cards because there was no rating severe enough.)

Attention at the convention was lavished on the famous lecturers, but it was also there for the not-so. Amateur speakers schmoozed with professionals, asking how to get on a minor lecture circuit, asking how to get an agent. There was the Rev. Olivia Miller, a self-professed energy channeler who spoke at Monday's Speaking Ladder competition, discussing various medical crises with Rodger McFarlane, director of AIDS training at Sloan-Kettering, who spoke Wednesday on America's response to AIDS. "I'm learning a lot here," she said. "I think everybody is."

It couldn't be helped -- a wealth of information was disseminated throughout the week on topics such as:

Cellulite: Remar Sutton on his journey from fat to fit.

Ollie and Ronnie: G. Gordon Liddy on the Iran-contra scandal.

Choking: Dr. Henry Heimlich on his life-saving maneuver.

Fang: Phyllis Diller on her cuddle-bunny.

How an Incurable Disease Almost Took My Life: Mary Kay du Pont on how she bounced back.

And, of course: Cholesterol and the Harvard Medical Report.

"People are fascinated with medical matters this year," Moore said. "It's a topic that's hot as hell."

Other "in" topics that Moore says are sure to burn up the nation's lecture circuit in 1988: numerology, anything dealing with the occult, anything dealing with religion (thank you, Jim and Tammy).

Some "out" topics: anything "fuzzy and inspirational," anything dealing with feminism.

"For some reason, women's lib is not a hot topic at the convention this year," Moore said. "We've asked people, and it's low on their lists."

Discussions revolving around the fees commanded by the nation's foremost speakers were also common at this year's convention, as they are every year. Some bottom lines:

Bob Hope: $40,000 a speech plus expenses. "Getting older helps," Moore said.

Gerald Ford: $15,000 a speech, plus airplane fees and security guards.

Hal Holbrook: as much as $250,000 for his "Mark Twain Tonight" speech/dramatic presentation.

Of course, not everyone was in it for the money.

ABC News correspondent Sam Donaldson, who spoke yesterday on his travails with President Reagan and then answered questions on Supreme Court nominee Robert Bork and Soviet relations, said he accepted the IPA invitation because, "Like that girl from 'Oklahoma!,' I'm just a guy who can't say no ... I guess I like to hear the sound of my own voice."

Donaldson added that the convention made him reflect on "exorbitant" fees paid today's speakers. "I'm from El Paso, Texas, son," he said. "You must remember that this still seems like a large sum to me." For all his amazement, Donaldson refused to say how much he collected after each speech.

Some speakers, such as gun control advocate Sarah Brady, wife of presidential Press Secretary Jim Brady, who was wounded in the attempted assassination of the president in 1981 by John Hinckley, came not for the money or the glory but to send a message. "I want to convince people to let officials know how they feel about the gun control issue," she said before her speech yesterday, adding that she hoped she would get some bookings out of her appearance. She asks for just enough money to cover her expenses, such as air fare and the baby-sitting fee she must pay whenever she leaves Washington.

"What we've been through," she said, "makes you rearrange your priorities a little. I'm not in it for the profit."

But for every Brady with a message, there was a Barrows with a motive.

After her speech, the latter shed a little more light on her priorities.

On her lecture marketability: She figures it's good for at least another year. "What with my book in paperback and the movie coming out, the topic will be hot through the fall and spring."

On her lecture following: She maintains that she is very popular with college audiences, although "homosexuals love me too. I have a huge gay following."

On why she is not using any of her speech profits to help get prostitutes off the streets: "I'm not a social service person," she said.