Brooke Shields says the only time she's ever worn a miniskirt was when "I was growing and my skirt got very short." But from the front row of the Yves Saint Laurent showing for Rive Gauche yesterday, where she was viewing the collections before a photo session for Harper's Bazaar, she thought the idea was pretty appealing. So were all the knickers, the black dresses, the long coats and velvet skirts.

And if it all looked pretty new to the 14-year-old star of "Pretty Baby," for the audience watching its fifth day of showings of the fall collection, the scene and the clothes were a bit familiar. But there were enough changes in the fashions to prod Arnold Aronsion, chief executive officer of Saks Fifth Avenue, to call it "a retailer's treasure."

Perhaps that's because Saint Laurent is best at what everyone has tried this week making styles fresh enough to have customers part with their dollars next fall -- and not rocking the boat.

Said Sonia Caproni, fashion director of I. Magnin, "You could pick up just the waiter's jacket with a double row of buttons, and wear it with what you already own. Or replace last year's panne velvet skirt with a smooth cotton velvet -- very flattering because it fits smoothly over the hips with a small yoke before it gets very full."

And for those who want to try something new, Saint Laurent offered coachman's and long velvet coats, variations on the black tuxedos or smoking styles, or sarong skirts in charmeuse.

Like other designers, Saint Laurent has played hs strong suits this season, as well as easy silk print or challis dresses, trouser pants or knickers. And for those who don't want to turn over big bucks for one-season styles, Saint Laurent showed lots of wearable black dresses with a noncontroversial dateline or hemline.

But for the old-timers, and there are quite a few who have watched Saint Laurent through his Dior days to the couture and current boom in his ready-to-wear, the collection became a bit of a game. When did he first do the Mondrian styles? When was the first smoking jacket? How about the first tiered challis printed baby dress, the first cowboy styles, the first ruffled peasant styles? If you didn't remember exactly, it didn't matter since the current version, while new, look familiar enough to be the original versions.

If the styles weren't familiar to Shields, a few of the models were. She had seen Pat Cleveland at Regine's in New York at a benefit, and had met Jerry Hall, girlfriend of Mick Jagger, so often she considered her a friend. "Everything Jerry wore I really liked," insisted Shields after the show.

Shields, who was wearing what her mother called "her Easter suit" -- a white belted jacket and pleated shirt from Alexander, a New York discounter -- was taking pictures during the show. She quickly realized she had no film in the camera and borrowed some from AP photographer Randy Taylor.

"I like suits best of all because they are a whole outfit," said the B-plus student. She says she wears suits most Tuesdays, which is "dress up day," at the New Jersey private school she attends. Other times she is in corduroy pants and sweaters. No jeans. The school doesn't permit it. Her mother reported that Brooke saw someone wearing an identical suit in the airport on the way over to Paris.

Brooke usually shops with her mother. "Her taste is much more conservative than mine," admitted Terry Shields, who was sitting two rows behind her daughter during the YSL show. Brooke would turn back to her mother for approval on the styles that caught her eye.

But neither Brooke nor her mother has any say in what Brooke will wear in Harper's Bazaar. Terry Shields is sure they will not choose YSL's see-through tops and see-through skirts. "I know we are in good hands," she said confidently.