It was a rare fashion show, indeed. The guests sat on gold chairs last night in the Tudor-style mansion that is the French Embassy residence. And the models, all brought from France, showed off the Guy Laroche clothes at a black-tie benefit for the Washington Opera.

But not a thing was for sale.

In fact, Dru Heinz, international socialite, who had seen pictures of the collection, called the designer in Washington yesterday to place an order for a dress. He turned her down. "Two weeks ago we took our last order on this collection. The house simply can't do any more business," explained the designer before the show. The clothes were his couture, made-to-order collection with prices that started at $2,500 for a wool dress, $3,000 for a little number in silk.

So why bring such a collection to Washington? To promote the perfume and the boutique -- there's one in the Watergate -- and to do some scouting as part of a 15-city tour of the United States for a future collection to be made in America. His partner for all his ventures is, he says, Baron Bich, of "Flipped Your Bic" fame.

"I already do too much business in Europe," said the designer, expressing a rare complaint these days. In his newest venture, by manufacturing and selling in New York, he will produce dresses far below the price of his French-made garments.

But if the audience couldn't buy the clothes, they had the unusual chance to see the intricately made and fully "accessorized" designs -- Laroche designed all the hats and shoes, as well -- that make up a healthy share of his annual $17 million business.

Nothing in couture is very simple. His suits, skirts or dresses are often made with tunic or double hems. His jackets and coats are frequently sculpted carefully in cocoon or blouson shapes; his dresses frequently have elaborate sleeve treatments; his colors -- particularly a deep electric blue that he often pairs with black -- are specially dyed for him; and his embroideries are masterworks of craftsmanship.

One woman who appreciates his artistry is Ethel Garrett, a Washington grand dame who sat with Denise Vernier-Palliez, the wife of the French ambassador. Garrett, who came to the show even though she recently recovered from a broken pelvis, was wearing a deep pink, beaded dress she had bought at Guy Laroche 24 years ago. Even Laroche stood in admiration: "I couldn't make such a thing today."