Yves Saint Laurent has restored neoclassicism as the look of the avant-garde.

In his collection shown on the last day of the presentations of clothes for next spring, Saint Laurent yesterday zeroed in on a new way to dress that is, in fact, a very old way to dress. He has done away with the super-lavishness he encouraged in recent seasons for simple, draped toga styles for evening, matte jersey and even scroll-shaped jewelry that resembles tops of Corinthian columns. The finale of his show featured three models in togas of red, white and blue.

Saint Laurent is not alone in his nod to the old as new. Claude Montana, who once shocked the fashion world with black leather blousons and pants, draped suede in a classical way and showed Grecian-inspired styles in pastel silk jerseys as the finale to his show earlier. (He has also just brought Corinthian columns into his new apartment along with modern Italian lamps and Ming tables.) And Thierry Mugler called one section of his show "Parthenon" and showed women in draped pastel dresses and wearing wreaths of flowers in their hair. Even Givenchy showed Greek borders on white dresses.

But some things don't change. As usual, the Saint Laurent show was the hottest ticket in Paris and the one that turned out the most posh crowd, including Paloma Picasso, the Baroness Guy de Rothschild and Helene Rochas. Carol Price, wife of the U.S. ambassador to Belgium and a friend of Nancy Reagan's, took the train from Brussels for the show and was seated in the front row -- "One of the advantages of being an ambassador's wife," she said. She was wearing a Bill Blass brown tweed suit with white pique' collar.

Saint Laurent supported his customers who already own many of his classic styles by providing new versions of the peacoat, the blazer, the tunic and the blouson, reassuring them that it was just fine to keep on wearing them.

But he refined many current ideas that have also been seen in other designer shows. He topped his sailor theme with a version of the enlistee's cap, and showed underwear as outerwear in dresses that looked like slips or petticoats. His double skirt, such as a turquoise skirt over a longer black skirt, is his way of adding color; his black lace skirt may be the replacement for his popular gold leather skirt.

He still likes Bermuda shorts and skirts the length of Bermuda shorts. But he also showed longer lengths for those who don't believe their legs are so terrific. And his pants that are banded like knickers can be mid-calf length, too.

To make up for the lack of embellishment, he showed much jewelry. Some models wore, at one time, three bracelets, a double pendant necklace and big earrings. He showed see-through black stockings and shoes -- often sandals -- embellished with stones. A signature of past collections, the black patent shoe, has given way to colored pumps with a contrasting color for the heel, or a pump with a scroll pattern on it.

"He has shown great restraint getting away from all that opulence in dressing," said Sonja Caproni, fashion director of I. Magnin, after the showing. "He was so recently involved in overstatement, now just wearing an oversized man's jacket and short skirt seems so sexy."

Like other designers, Saint Laurent showed a lot of clear colors but also, as usual, a lot of black. One unexpected use of color he's added is a dab of red to his hair.

And Saint Laurent may well be seeing an astrologist -- his favorite patterns are zodiac signs, stars and maps of the planet. In any case, it would be safe to predict a secure future for the designer.