When Eulabee Dix painted the portrait of Mark Twain that now hangs in the National Portrait Gallery, he left the choice of what to wear up to the subject.

"We talked of the independence of one's taste in dress, and Mr. Clemens and I agreed that people should wear what they pleased if they very much wished to," Dix once said. "He liked his white suit -- not because it was a white suite, but because it somehow suited his fancy."

Last night's guests at the Smithsonian's Contributing Members' third annual ball were given the chance to wear portrait dress, from 17th-century Pocahontas to the Apollo II astronauts.

It was a bow to the fact that the ball this year was held in the National Portrait Gallery's Great Hall, in keeping with the hall's elaborate Victorian style.

Not all guests sought to copy portraits hanging in the gallery. Sara Blunt, a Georgetowner active in local politics, wore the Edwardian dress with pleats and a bustle that her grandmother, Sarah Thompson Conrad, wore for a portrait.

John Daniel Reeves, an attorney, took on the pale, double-breasted suit style of Huey Long, and dancer/choreographer Murray Spalding opted for a Scarlet O'Hara style dress with big floppy hat.

According to research historian Margaret Christman, not all subjects wore the clothes that appear in their portraits.

When Douglas Chandor painted Sir Winston Churchill while he posed at the Waldorf Towers in 1946, Churchill was wearing his favorite zip-front jump suit and slippers. In the portrait he is garbed in full regalia of a military uniform. "There is no doubt about it, polished buttons, insignia and perhaps a ribbon or two do help a fellow," said Chandor.

Several portrait artists insisted on having the last word on what the subject wore. "I don't want people to look at my pictures and say how beautiful the drapery is," Gilbert Stuart once said. "The face is what I care about. I copy the works of God and leave clothes to tailors and mantua-makers."

At least no guest at last night's ball, at which black tie was an option, risked the fate of a George Gershwin portrait. Gershwin's mother was offered her son's portrait by artist Arthur Kaufman, but because Gershwin was wearing the kind of informal dress his mother disapproved of, she turned it down.