"You hear so much talk of investment value these days. I've never thought of my antiques as an investment. I can't sell. And here I am still buying."

Mrs. Richard Dunn was in the midst of temptation as she chatted before one of the 44 dealers' booths at the 22nd annual Washington Antiques Show preview opening for sponsors.

In the browsing crowd of more than 500 were the real collectors of antiques, those with the taste, dedication, and money to support their habit. For them the beauty, proportion, and craftsmanship of a Chippendale secretary or a Connecticut cherry highboy evoke the same thrill of pleasure that a champion blood line does for a dog or horse lover.

"But the fabulous price appreciation of recent years does help justify spending money for old antiques to those who don't understand - and also to yourself," said one of the preview sponsors, looking every inch a hard-headed business executive. He was looking at a cup and saucer with a price label of $110.

For dealers, antiques represent a business (a $3 billion-a-year business in the United States) and not a love to be indugled. Dealers size up collectors as the collectors size up the dealers' offerings. Both have a practiced eye.

"Where else can you have an investment that appreciates steadily and still have such pleasure in having it?" asked William B. Dennis, co-owner of The Virginians shop in Fredericksburg, Va.

"Why, one gal bought a marble top mixing table from us three or four years ago. She called recently, had remarried, and was moving and wondered whether we would buy it back. We gave her about 10 per cent a year on her original purchase price."

Dennis and his partner, Walter Angel, have been coming to the Washington Antiques Show since 1965. They've seen their fellow dealers "get older and grayer," prices keep jumping upward, and changes in the taste of Washington antique buyers.

"They're now much more discriminating and sophisticated," observed Dennis.

Only a few minutes after the preview opening, Dennis already had sold a sandwich whale lamp in blue and white for a "little over $1,000."

"Make that blue and clam-broth. It sounds better," he smiled.

A young man in a red waiter's coat and young girl in office attire stopped and aked the price of a brass candelabra.

"That's $475," said the dealer.

"Is it solid gold?" the waiter asked in wonderment.

Oscar Menendez, the waiter, and Ann Weichbrod, a hotel cashier, had taken their break for a visit to the antique show at the Shoreham American's Regency Ballroom.

They missed the two Chinese porcelain dogs, certainly pleasant enough but not that distinguished-looking to the non-discriminating eye. Perhaps two feet high, or a bit more, they were sitting on a lovely table in Booth No. 24, that of Fred B. Nadler, of Bay Head, N.J.

"The price for the pair is $70,000," explained Richard Trotta. "It's the size that makes them so valuable. They're Chinese exports, from 1770 or therabout. Now, those much smaller dos there, a pair would be a mere $9,500."

And who pays $70,000 for a pair of porcelain dogs - museums?

No, there are individual collectors who buy such items and pay such prices, according to Trotta.

"Some collectors live in homes like museums," he added with an understanding smile.

Trotta purchased the Chinese porcelain dogs from a dealer in Londn. Portugal, once a clearing-house for Chinese exports, is now depleted. You can buy all the items you want, Trotta pointed out, but you can't export them.

One reason for the export ban, he said, seems to have been that a former regime did not want the old families to sell off thir treasures and turn to Swiss bank accounts.

But, beyond the vagaries ofpolitical regimes, more and more countries have been enacting laws to protect national treasures from being drained off in the export market. And that makes it harder for antique dealers to find prize pieces overseas.

In this country, museums are buying more and more items, removing them from the antiques market. By now, the country auctions have sold most of the family attic heirlooms - and sometimes even the barns themselves, for the wood.

But antique dealers still keep locking for the lucky find at an auction or estate sale.

John C. Newcomer, a tall strapping young man who sells antiques at Harpers Ferry, West Va., on weekends and "by appointment or chance," found a Joshua Johnson portrait at a state auction at Charleston just five miles away.

"It was in poor condition and hadn't been taken care of. We spent a lot on the restoration," he said, declining to say what he paid for the painting.

Newcomer finally persuaded a friend to sell him a Connecticut Valley chest from the 1720-30s period and has it on sale for $5,500.

"It's an original and hasn't been touched by a restorer. That's what the young people, and they're turning to collecting, want - the original finish without restoration."

The Washington Antiques Show is one of the big shows on the East Coast circuit. It is outdone by only two or three others, including the East Slide House Settlement Winter Antiques Show in New York City.

"And, of course, there's the West Coast. And don't forget Houston with all that new oil money," said one dealer, recounting his travels on the show circuit.

The local show benefits the children's health service charities of the Thrift Shop. It will be open from noon to 10 p.m. today and from noon to 6 p.m. on the closing day. Tuesday at the Shoreham Americana. Admission is $3.

Mrs. Dunn, who was co-founder of the show 22 years ago, remembers that the sponsors tried to "buy a little something from each booth" to ensure success that first year and to make it worthwhile for the dealers.

Mrs. Dunn gave many of her antiques to her children when she moved from a 20-room house to an eigh-room house.

"That's another reason for justifying spending more money than you have - that you're passing on a heritage to another generation," says Lydia Preston, who has been the publicity director for this year's event.

But sometimes it's a little difficult to pass along the torch. Mrs. Dudley Owen (who was the publicity director for the first show) remembered a friend who wanted to give antiques to her daughter.

"The girl was into Scan furniture and wasn't interested. Her mother gave prize antiques to the Hermitage museum at Andrew jackson's birthplace in Tennessee. A few years later, the daughter asked her mother for some of the pieces, but it was too late."

The social world always finds a fashionable center about which to congregate - tennis, horses, and antique shows for instance.

The old standbys came to this year Washington Antique Show. There was Mrs. Robert Low Bacon, leaning on her cane. There was Mrs. George Maurice Morris, who was described as having assembled her Washington home. Lindens, "piece by piece from New England."

But it was the younger members of the Thrift Shop committee that put together the show - Jane Roberts DeGraff, the chairman: Mrs. C. Jackson Ritchie Jr. and Mrs. Brainard D. Christopher S. Sargent, secretary.