Ah, the little black dress.

"The little black dress can be chic, conservative, sexy, arty or artistic," says Kathleen Mitchell.

A costume collector from Washington, Pa., Mitchell brought a sample of her collection of little black dresses to Annapolis this week. Members of the Caritas Society of St. John's College and a couple of students paraded in the clothes before guests at the school's Key Auditorium to raise money for financially needy students.

The "little black dress started in the 1920s in the French couture with Chanel and hasn't stopped since," Stella Blum, curator of costumes for the Metropolitan Museum of Art, said recently. "Every woman had to have one in her wardrobe."

Both a social equalizer and a season spanner, the "little black dress" became regarded as sophisticated and appropriate for all occasions. And like the tuxedo, the LBD survived fashion trends.

"I always wore a little black dress when I wanted to make an impression," said Anna May Wilson, secretary of the Caritas. "In 1942 I had one in college. I got my husband while wearing one."

"At one time there were occasions that I felt required a little black dress so I always had one in my wardrobe," said Marilyn Funderburk, former assistant White House social secretary. "Even now, although I feel I can wear other things, if I'm not sure what to wear I pull out a black dress and can be sure it will be appropriate." She still occasionally wears the black lace dress by Bill Blass she bought in 1970.

Mitchell's black-dress collection stretches back to the turn of the century with widows' weeds from 1896 -- "You can tell she had been in mourning about three months since the veil is lighter than if she had just gone into mourning." The show also included a shirtdress style that might have been worn by suffragettes, flapper dresses, bias dresses of the 1930s and a black bridesmaid's dress of about that time, a daytime wool by Adrian with signature broad shoulders, theater suits from the 1940s, dress and jacket costumes of the 1950s, a mini dress (that looked remarkably like a hooker's) and several spinoffs from Courre ges from the 1960s. The finale was a club member wearing her new Neiman-Marcus black velvet suit and mink muff.

"You have to be of 'a certain age' to know about the little black dress," says Grace Mirabella, Vogue's editor-in-chief, who remembers versions by Norman Norell, Balenciaga, Donald Brooks, and the Kimberly Knitwear knock-offs of each of them. "It was the answer to the perfect thing to wear when you were going out, with another possible option being the Chanel suit." It was Audrey Hepburn and Givenchy who established pearls as just the jewelry to wear with such a dress, said Mirabella.

What Thursday's show lacked in historical accuracy it made up in entertainment. As the volunteer "models" postured and posed in a caricature of the period of the dresses they were wearing, who noticed, for example, that the shoes were from decades later? The audience was delighted to cheer its chums in black taffeta and pearls sashaying along a runway framed in red poinsettias.

Mitchell, who also is curator of the theater collection of Washington and Jefferson College, acquired her own collection through thrift-shop purchases, country auctions and donations. A black velvet dress from 1908 just happened to be tucked in a suitcase she got for a $3 bid at an auction, she said. It occurred to her that she could track changes in style and silhouette through her black dresses, which she said make up a third of her 500-piece collection, after reading Anne Hollander's "Seeing Through Clothes."

She pegs the demise of the LBD to the late 1960s, when black became part of the anti-fashion statement of beatniks and artists. "Now with the return of a more ordered way of life, the mystique of the black dress will work its way back into fashion," she told the audience.

Designer Bill Blass, whose black dresses are seldom little in price or silhouette, said from New York that the black dress fell out of favor only when heels and hems were lowered simultaneously, making the black dress "glum and dour." But they are back, he says, "because of shorter hems and sexy shoes."

Deeda Blair, who is on everyone's best-dressed list, recalled fondly a black nubby wool dress and jacket by Balenciaga that she had in the 1960s. "I must have worn it a million times," she said recently.

In her closet now is an aubergine velvet suit from Chanel that she has worn for seven years, but she thinks the little black dress is due for a revival. "People may have to go back to it with the economy the way it is these days," she said.