The best way to face the coming season is backward.

Designers have made the exit as grand as the entrance with bare backs, back buttons and even bustles--yes, bustles.

"A bare back is very sexy," says designer Bill Blass, "and women are looking for sexy clothes this season."

That's undoubtedly the appeal of the emphasis from behind. When clothes are fitted, as many are this season, the fanny becomes more important and with it, back slits on skirts and back buttons, all a kind of 1950s sexiness that hasn't been around in a while.

But bustles? Adolfo called the bustle-like detail on the dresses he showed in his new collection recently "poufs," attached them to belts and filled them with tulle. He did it to be different, he said. "I've been making clothes since 1967, but putting the emphasis on the behind is a novelty for me," said the designer, who added that the shape reminded him of the cover of a Barbara Cartland novel.

Adolfo's new designs also look like some of the Belle Epoque gowns currently on view at the Metropolitan Museum of Art and worn by some of the guests at the celebration of the exhibition opening. "It is a terrific feeling to wear them. It makes you feel like a different era and feel like a lady again," says Pal Henry, Adolfo's top model, who opened the show in a gown with a pouf.

They won't be worn only on the runway. Betsy Bloomingdale has ordered her bustled gown from Adolfo to wear when she meets Queen Elizabeth II on her visit here. Barbara Davis, wife of the head of 20th Century-Fox, and Nan Kempner, a New York clothes aficionado, have also put in their orders for dresses with bustles.

Added Ellin Saltzman, fashion director of Saks Fifth Avenue, "Thank goodness the bustles are detachable."