Some are courtly, some are testy. They wear cowboy boots, Savile Row suits or jeans. The luxuries they sell are functionless and expensive. Often they are ridiculed, as parasites or worse, by the artists and collectors who, though they cannot do without them, begrudge them their 40, 50, or 60 percent commissions. Are they enthusiasts or teachers, hustlers or historians, salesmen or sharks - or all of the above?

They are a curius crew, the dealers, the peole who sell art.

London's Nicholas Treadwell, for example, was a cup-and-saucer salesman when one day his girl friend started drawing on the table cloth. "I thought, Good Lord, how wonderful! Why be supplied by factories?" Abandoning his china, Treadwell started selling art.

Hundreds of other dealers from around the world are in town this week for "Art '78 Washington" at the D.C. National Armory. Part marketplace, part fair, part art dealers' convention, it will remain open to the public through Monday afternoon.

The dealers will you that they love their work, though their reasons vary. It cost them much to comer here - $800 for each booth, more for framing and insurance, restaurants, hotels. They deal with large sums, with $1,000 etchings, $100,000 paintings, yet most of them confide they are not in it for the money. There is no school for dealers. Some of them were furriers once, or engineers, or translators, or, of course, collectors. Their backgrounds are as varied as the works of art they sell.

The dealer, in his gallery, is the master of the house, the host, the ruler of the roost. It is different at an art fair. The public is no problem, the dealers all are used to that. "We'll sometimes get 5,000 visitors on Saturday, they come to Solto by the bus load," says New York's Louis K. Meisel. Dealers, at an art fair, rub elbows with their competitors as well.

The booths are small and crowded the countless works on view have been hastily installed. Lithographs and oils, tapestries and drawings, masterworks and shlock - the mind begins to blur. Yet each piece has a champion, a dealer who believes in its historical significance, its beauty, and its worth.

"Good art sells itself," says New York's Neil Printz. His collegaues says the same, but it is not easy to believe them. In that cacophany of images it is thedealer's speech, his confidence, his presence, that guides that overloaded, undecided eye.

Printz worked once in museums. He helped organize the Rauschemberg retrospective here at the National Collection of Fine Arts. Now he works with Holly Solomon, in SoHo. "People tell me that by going into commerce I've stepped down professionally. I don't believe them. I'm learning. I'm seeing things I'd never see in the rarefield museum."

Holly Solomon seems anxious. Her anxiety is shared by many of her colleagues, but most of them disguise it. "When I was a collector, and not yet a dealer, I'd sleep until 11. Now I'm up at 6. It's called anxiety. Many artists have to eat. That's called survival. It's the selling that I hate."

Solomon's displeasure is shared by many of her colleagues who say they love their art, their artists, their collectors, but that selling is a drag. Jim Rudolph says he likes it. Rudolph sells the work of one artist only, a Spaniard, Berocal. Berrocal's shiny sculptures come to pieces like so many chinese puzzles. Rudolph can assemble them with extraordinary speed. "I know more about Berrocal than anyone but Berrocal," says Rudolph. "I'm so in love with this man's work I'm having the time of my life."

Rudolph was an engineer before he turned to art. Jacques Kaplan of Manhattan, whose booth, by museum standards, is the class stand at the fair, was once a Fifth Avenue furrier who began his collection by trading minks for art.

"I must have traded 700 coats," he said. "It is a nice way to acquire. There is something very cold about giving checks for art." Kaplan does not "keep a shop." He is a private dealer, who also hates to sell. "I have three charming assistants. They do the selling for me."

"In America," says Kaplan, "dealers, on the whole, are relatively honest. In the fur business, as in diamonds, if you do a dirty trick you are out of its for life. That is not true in art. In Europe there are many dealers I regard as sharks."

"Kaplan is quite right," said Peter J. Lenart, another private dealer, who operates from Paris. "I live there, but I will not sell there." Instead Lenart travels, to Switzerland, Sweden, Greece, South America, Iran. Lenart, in a sense, owes his career to art fairs. It was in Basel, while working as a translator (he speaks German, French and English) and being paid with drawings, that he first turned to art.

"The good dealer," says Lenart "sells his credibility as well as his art."

"Let's be straight about it," said Louis K. Meisel. "When that painting is on the easel, it's art. When it's in my gallery it's merchandise." But the coldness in that statement is a bit misleading. Meisel, and Susan Pear Meisel, his wife, provide more than merchandise in their enormously successful downtown New York gallery. They also offer hospitality. They give parties for 300, sit-down dinners for 50. When the downstairs doorbell rings (they live above their gallery), even when it's 2 a.m., the ringer is often asked up.

"All my clients are my friends; all my artists are my friends. It is at 4 in the morning that the biggest works get sold."

"I hate being hustled. And I hate hustling," says Max Protetch of New York. "I love the action, the selling, the explaining," says Sam Markle of Toronto's Electric Gallery, where all the works on sale are powered by electricity. "What I hate is the dumb questions, and the superficiality," says Ihor Holybizky, who works with Markle. "You are not selling a necessity. It's not something people need. We are dealers in both senses. We're feeding a habit. Buying art is a compulsion. Once you've started, you can't stop."

Elias A. Felluss organized the art fair and has learned from his mistakes. This year's fair, the third, is better than the escond, which was better than the first. It is not this people that drew him to the business. "Some of them are pretty hopless, and it's not the art they bring," says Felluss, who is, in every fiber, an entrepreneur.

At 14 he was selling hot dogs on the beach. he has been a dress designer, too, a TV station employe, a waiter, a logo designer and a dealer - in that order. Now he runs an art fair for dealers form Bulgaria, San Francisco, Hamburg, London, Paris, Deerfield, Ill., Israel, Milan.

Felluss's voice was hoarse. For hours he had been trying to solve the usual art fair problems: the drapes were the wrong colors, the light didn't work, the crates were in the way. The public address system had just told the dealers that one of them, Washington's Diane Brown, had just given birth to a 7-pound boy. Named Joseph. For her father.

"Hey, no hype," said Felluss. "We're serving the free world."