"I don't ride," said Martin Malarkey, the president of the Washington International Horse Show. "I'm a business man. I was asked to be on the board. I pointed out that I didn't know the first thing about horses, and they said, 'That's all right. We need to start to make some money off this thing.'"

So Malarkey, a cable television management consultant, turned out in the horsiest of Harris tweeds yesterday for a hunt breakfast at the British embassy.

It was the kickoff for last night's opening of the International Horse Show which benefits the Girl Scouts of America, at the Capital Centre.

It's hardly even very horsey any more. You don't need to own a horse or shirt studs shaped like foxes or even an old society name - just contribute $180 and voila, you were invited to a weekend's worth of parties, beginning at the Italian embassy Friday night. CBS vice president Bill Leonard was there, among the 150 dinner guests, "because of business," he said. "Part of my job is to go to these things once in a while, and, besides, this lady who's here with me is a fan of horse racing and also a friend of mine." He referred to his wife, Cappy.

One of the attractions may have been noted horsewoman Elizabeth ("National Velvet") Taylor, whose name pops up these days on more Washington benefit invitations than you can shake a stick at. Taylor and her husband, John Warner, were co-chairmen of last night's white-tie opening, but they failed to show earlier at the British embassy.

A hunt breakfast consists of Bloody Marys, screwdrivers, Irish coffee and steaming silver chafing dishes. There are women in designer suits and tweedy gents bearing off plates that are piled high with ham and biscuits - traditionally, it is thought, they are famished by the morning's brisk ride.

"I used to ride," said Vicki Bagley, a Carter supporter and the owner of a Georgetown realty firm. "But I was no good. That's why I don't ride any more," Bagley was wearing a 3-year-old jacket, thrown together with a few threads from the Yves Saint Laurent boutique here. She eyed her outfit deprecatingly, "I don't know what a hunt-breakfast dress is either. I'm not very horsey."

Mrs. Howard de Franceaux, wearing a plumed Paris hat, said she didn't ride, and her husband didn't either. "I used to be the couture buyer at Garfinckel's," she said. "I majored in social work, but I found it too depressing. So I became a social worker among the rich."

The diamond stick pin in Judi Lewis' ascot was, she said, "Tiffany's, I think. Oh, it was a gift, of course. One should never buy those things for one's self." Lewis was dressed in what might have been a soigne riding habit. It was, actually, a Geoffrey Beene suit worn with Charles ("Big BUcks") Jourdan boots, with 5-inch spike heels - just the thing for the paddock. Lewis, who is executive director of Washington's Media Institute, said she learned to ride at Middleburg but no longer has the time.

On the terrace of the British embassy, in a sort of gray flannel jockey's cap, was Helen Polinger, widow of Maryland builder Milton Polinger. A race-hose breeder, she is a connoisseur of hats; she wore a big floppy hat to testify about the ownership of the Marlboro Race Track in the second trial of former Maryland Gov. Marvin Mandel.

"My husond trial of former Maryland Gov. Marvin Mandel.

"My husband was interested in horses." she said."We got married and I got an interest in them, too." In addition to herPolinger Through-bred Farm in Olney, Md. she rides with the Goshen Hunt and is now "trying to campaign a stallion named Anticipation. I'm anticipating," she said smiling, "he'll do very well."

Staff writer Nancy Collins also contributed to this article.