"I like a girl who is an uncut diamond -- one I can cut and polish," says 43-year-old Michael O'Harro, who has polished more gems in his bachelor life than most. During two decades as the owner of singles bars and discos in Washington, he has dated hundreds of young women-- and the operative word here is young, as in 18 to 20--who grew up to be models, Hollywood sex bombs and men's magazine centerfolds.

Is this any way for a grown man to behave?

"I like young women," he says. "They make you feel younger. They're not leading the humdrum life of a housewife in curlers whose whole excitement all day is watching 'The Young and the Restless.' They're much more trendy and less inhibited. And they are definitely firmer of flesh."

When he was young, O'Harro chose his college (University of Arizona) because he wanted to "major in partying," and he hasn't switched majors since. As a Navy ensign in Washington in 1964 with only a '55 Thunderbird for company, he rented halls and organized singles parties so he and his friends could meet women. That led to a career as owner and promoter of singles bars and discos. In fact, he is credited by William Manchester in his social history of the United States, The Glory and the Dream, with having invented the single's bar. It's a footnote that some dispute, but there's no denying O'Harro's maiden effort in the '60s, The Gentlemen II, was one of the first bars in which many men and women went with the then-revolutionary idea of finding someone to take home that night. And until it closed last year, O'Harro's Georgetown disco called Tramp's was one of the most successful of its genre.

Today, as he plots to open another restaurant and bar, Champions, later this year, O'Harro lives in an Arlington home replete with a tiger skin on the wall, a hot tub in the back yard, and a Ferrari, Excalibur and antique Cadillac convertible in the driveway. It is the lair of a Don Juan, a confirmed bachelor whose credentials include having been named Cosmopolitan's Bachelor of the Month in 1976 and one of America's 10 most eligible bachelors of 1977 by the National Enquirer in a list that also included Jerry Brown.

Such credits are perhaps far from winning a Nobel, but O'Harro likes the attention. He carefully catalogues all press mentions and is so organized he still has the addresses of the more than 600 women he has counted as lovers in his life. Not that you should get the wrong idea.

"The bedroom is not a sporting field for me," says O'Harro, "and I don't consider experience or lack of experience to be of importance in bed because it's an emotional feeling. I don't sleep with someone just to have sexual gratification. I sleep with people I like and who like me."

Sure, you're saying to yourself, but when you're 43, isn't it difficult to find something to talk about with women two decades younger?

"I like to encourage them to grow," answers O'Harro. "I had a girl one time who didn't know what year Columbus discovered America. I don't think of myself as a Svengali, but I'm sure there are certain similarities here.

"Most of the women I meet are in their early 20s. They're not looking for that white picket fence. Especially on that first date, they want to have a good time--they're not chasing fantasies, they're living them. I don't want to get involved with girls who have a bad image of men. In other words, as women get older, unfortunately, they probably get married. Especially the beautiful ones. And then, if it's a bad marriage, they have a feeling men they meet are like their previous husbands, and you have to go through a process of convincing them you're not the same SOB they were married to.

"I also don't like all the baggage of a woman who has to worry about baby sitters and can't go on a holiday to the Caribbean and this and that. I like the ability to be full of adventure--at the last minute you can call them and say, 'Let's go to Atlantic City!' and they'll say, 'Great, let's go!'"

O' Harro knows exactly what you're thinking: Hey, what a guy! But what's in it for him?

"All my former lovers in my life are my friends, usually my best friends," he says.

O'Harro gets a kick out of seeing his former girlfriend, Twyla Littleton, in commercials she's made since moving to Los Angeles to pursue a career as an actress. His heart swells with pride when he opens the pages of Playboy and sees as a centerfold Dorothy Mays, a young woman he spotted in a Baltimore movie theater and then propelled toward a career in modeling.

A typical O'Harro first date often includes dinner at The Prime Rib or the new steakhouse in Georgetown, Morton's. When he has a club in operation, O'Harro might take his date there afterward, or to F. Scott's or his home. And then to the bedroom?

"If the lady is interested in that," he says, "but I'd never suggest it. You let things happen as they occur. It's not of major importance to me, though it very frequently happens. Many serious romances I've had, they have slept with me on the first date. If they live at home, obviously they don't spend the night."

Don't think all this unbridled hedonism doesn't have its slower moments. O'Harro's latest serious girlfriend, beauty pageant winner Lori Estep, is now just a good friend, and O'Harro is "lonely right now because I don't have a special lady."

But a playboy asks for all that.

"Loneliness comes with the job," he says, "and it's not a negative thing, like I'm sitting at home feeling sorry for myself. I can go out every night of the week with a different girl, and at the moment I'm dating a couple of very nice ladies. But I don't have anyone who is a superstarrin my life."

Things are tough all over, O'Harro. Maybe it's time for a Don Juan's thoughts to turn to marriage?

"I'd rather be lonely," answers O'Harro without hesitation, "than unhappy."