Preview dinner guests at the Washington Antiques Show at the Shoreham last night were mostly the sort of people who had antiques at home as good as the ones for sale.

As historian Douglas Sprunt put it: "I don't dare look. We're about at the point where we need to be rid of some instead of buying more."

The evening is traditionally supported by Old Washington, some of whose families came to the area before the Capitol did.

Every year, Clement Conger, curator of the White House, the State Department Fine Arts Collection and Blair House, can be found at Elinor Gordon's booth of Chinese export porcelain. This time, he walked away with a pair of cider jugs -- the match for a bowl already in the State Department's Diplomatic Reception Rooms. The set was originally owned by John Jay, the American minister of external affairs and the first chief justice.

"I bought it on credit," said Conger. "Now I need to find a donor to put up the $20,000 for them. I'm already a million dollars in debt on the latest remodeling at the State Department, for the secretary of state's office and the Benjamin Franklin Dining Room."

Some wondered, with Omar Khayyam, what the vintners buy half so sweet as the stuff they sell when they saw the contingent from Sotheby's New York auction house: Joan Tobin with husband Maurice, Oatsie Charles of Washington and William W. Stahl Jr. of New York. In the same category was Harold Keshishian, the rug collector and dealer, who bought an antique seraph rug during the evening.

Judith Waldrop Frank is coauthor with Sprunt of the Junior League's "The City of Washington: An Illustrated History," as well as a former cochairman of the show. "You know, this show is a great amount of work," she said. "That's the reason the cochairmen are usually women who've never worked on the show before. You need a virgin to jump down the volcano."

"Ours is different from the New York Winter Antiques Show," said Donna Blackburn, who has helped with the show for several years, "because ours is produced by ardent amateurs instead of paid professionals."

Charles B. King, husband of Lianna Rose King, one of this year's chairmen, said that indeed, it was true he was there to keep her from buying anything. "But we'll need everybody here to keep her from it."

The other cochairman, Jean Ann Bostwick, and Jacqueline Anne Thompson, preview dinner chairman for a second year, dutifully stood at the door greeting people, but occassionally escaped to admire antiques such as the circa 1860 Louis XV French ormolu-decorated desk.

Some people were exhibits themselves. Edie Poor had on a magnificent silver necklace, a spray of flowers that embraced her neck, made by Betty Helen Loughi, a Maryland silversmith. Retired rear admiral Walter Innis and his wife, author Pauline Innis, stood for a while by the booth purveying paintings of sailing ships.

Attorney Leonard Marks and writer Dorothy Marks admired a red tole tray, but a sold sign was slapped on it before they could decide.

The 1,000-strong black tie and dinner dress crowd ate in two sittings so the 46 dealers wouldn't feel neglected. The dinner ended in fireworks -- a spectacular rum-flavored pastry was brought in ornamented with sparklers.

The show includes "Washington Remembered: A Legacy in Historic Preservation," an exhibit of artifacts, drawings and photographs, as well as a five-day symposium on historic preservation, with lectures and tours.

The Thrift Shop Charities: Child Health Center Board of Children's Hospital, the Children's Hospital National Medical Center, Columbia Hospital for Women Medical Center, the Hospital for Sick Children and St. John's Child Development Center benefit from the event.