The juices of enterprise were at high tide the third Tuesday of July three years ago. They carried Tom Gentry into a patchwork sport coat so loud that small animals covered their ears and burrowed into the bluegrass hills. Then, in harmony with the entrepreneurial drums he hears, Tom Gentry asked the tiny, beautiful Japanese woman if she'd like to dance.

The third Tuesday of every July is the day Tom Gentry gets rich, if he's going to, for then the best breeders of thoroughbreds bring their best yearlings to the Keeneland sales. On that day three years ago, Gentry brought a colt by the great runner, Hoist the Flag. He figured $200,000 was a fair price and (dream on) $500,000 would be better.

The Japanese group, a dozen gentlemen new to Keeneland, liked the Hoist the Flag colt. Gentry had given them dime-a-dozen rulers and pens bearing his name. He noticed they kept coming back to see the yearling. They remembered him, yes, the laughing American who danced with Rita Mae (to make up a forgotten name). And, ho-ho, see his funny coat of a thousand colors.

The third Tuesday of July 1980, Tom Gentry sold that yearling to Japanese investor Kazuo Nakamura for $1.6 million, then a record.

In the very proper auction pit at Keeneland, billionaires sit in pinstriped silence. Gentry leaped screaming into the arms of Nakamura. Next thing you know, Gentry, who is 46, redheaded and redfaced, stripped off his bizarre patchwork coat and put it on the Japanese gentleman. For $1.6 million, you get a coat, too.

"When I danced with the lady, the other breeders--they can be snobby around here, they don't have any fun--said, 'That SOB'll do anything to sell a horse,'" Gentry said today.

He smiled. "It worked, didn't it?"

The Kentucky Derby comes up Saturday. Little old ladies in Dubuque may believe the Derby is for cute horses gamboling in the sun. For Tom Gentry, and a thousand other horsemen at the top of the racing industry pyramid, the Derby is a high-stakes craps game in which one roll of the dice can make you rich, if not forever, at least for tomorrow.

Gentry is the breeder of Marfa, the likely Derby favorite Saturday. He arranged the blind date three springs ago that allowed his nice mare, Gray Matter, a fling with the Derby winner Foolish Pleasure. The result was a gray colt that Gentry sold at Keeneland two years ago for $300,000. Today, that colt is named Marfa.

A victory by Marfa wouldn't put cash in Gentry's hand. It would, however, turn up his substantial reputation another notch. Interested buyers know that on the Tom Gentry Farm, with the ribbony white fences and red gates, there is a yearling half-sister to Marfa.

"She's worth $300,000 today," Gentry said. "If Marfa wins, it's $1 million."

Quickly we should add that Gentry seldom errs through understatement. In a business long controlled by an old-boy society network, he is the kid from the wrong side of town. He calls himself "the maverick of the bluegrass." So first he had to sell his name (on rulers, pens, balloons). "Some wild 'maverick,' huh? Bumper stickers are wild? Only in contrast to folks who don't have any fun."

When they knew who Gentry was, he had to sell them good horses.

"Warner Jones and Leslie Combs (two old boys) had every buyer wrapped up," Gentry said. "Combs would put 'em in an armored truck and drive 'em straight from his house to Keeneland to buy his yearlings. After a while, Tom Gentry-breds started to beat Combs-breds. That got 'em out of his truck."

Gentry's father, Olin, worked 60 years as farm manager at three of Kentucky's great farms. He helped send out nine horses that won 13 Triple Crown races. Olin Gentry first was a rider. At age 13, three days after Pancho Villa terrorized Juarez, Gentry rode races there.

When he was 13, too big to ride and determined not to be a trainer, Tom Gentry bred and sold his first horse for $11,000.

"I'd seen my daddy make all that money for all those other people," Gentry said, "and so I said why not make it for ol' me."

It costs Gentry $1 million to run his 550-acre farm with 75 mares and maintain a stable of 22 racers. His income, in a good year, is twice that. There are 35 foals at his place now; maybe 15 of them will be good enough to go in the high-bucks Keeneland sale, where a $100,000 price tag is under average.

"The romance of this business begins and ends on the third Tuesday of July," he said. "Imagine any other business where your year's success is dependent on two hours of a July night."

Charles Engelhard, the late billionaire, once used loose change, $7,000, to buy a Gentry yearling and said, "That was to pay for all those damn pens and pocket knives I've gotten from Tom over the years." Engelhard also paid more than $100,000 each for three Gentry fillies.

Every July, Gentry and his wife, Kathy, put on a party in their backyard for a thousand friends and prospects. Last summer, they flew in Bob Hope. Chubby Checker works the Gentrys' Derby Day party at Churchill Downs this weekend, with some guests delivered by Gentry's helicopter.

The other day, the helicopter rose off the rooftop of a Lexington building for the flight to Louisville.

"I want to see how long it'll take to get the president to my party," Gentry said of his weekend house guest, Jimmy Carter.