The streamlined, seemly style of Britain's future queen is resonating with scores of young women who aspire to a classically patrician look but who have had few credible role models.

The influence of Catherine, Duchess of Cambridge, formerly known as Kate Middleton, was felt on the runways during New York Fashion Week, which ended on September 15. "We are in a Kate moment," said Ed Burstell, the managing director for Liberty of London. "Everyone wants to look like her, to act like her, to be her."

Seventh Avenue designers as diverse as Vera Wang, Tory Burch, Peter Som and Tommy Hilfiger have acknowledged her influence.

"We are definitely returning to a time when we want things that are more timeless and polished, not looking a mess," said Rachel Zoe, the stylist turned fashion designer whose fame once rested on a disheveled approach to dress. The duchess represents a return to classicism, said Ms. Zoe, who offered "Savile Row-style" tailoring and herringbone tweeds at Fashion Week.

"Now people are interested in looking ladylike," said Jason Wu, whose current concept of chic entails "an old-school silhouette," shapely and controlled but voluminous at times, reminiscent of a princess in a fairy tale. A couple of years ago, the deliberately dissolute look of a model off duty was a strong inspiration, he said.

Mr. Wu, who first gained recognition when he dressed American royalty in the person of Michelle Obama, sees fashion becoming more refined and less aggressive, he said. "The duchess is part of that," he said.

Mr. Hilfiger paraded Macintosh fabrics and Prince of Wales plaids on his catwalk. He said he was being "very studied" about how he was putting outfits together, to the point of offering matching shoes and bags. Kate's impact, he said, is all but inescapable: "She will influence all markets."

Chain stores like Zara, Reiss, Talbots and Topshop are already catering to a taste for replicKates, as bloggers have called them: pert shirtwaists, lace sheaths and primly tailored coatdresses.

Nor are the affluent immune to her charms. "We are not necessarily going to see exact adaptations of what she is wearing," said Ken Downing, the fashion director of Neiman Marcus, but she wields an impact just the same. "Dressing up is the new cool, and dressing down is old school. I attribute much of that to Kate."

Despite her popularity, the duchess has detractors. To describe a collection as "very Kate Middleton" can signal disdain for the sort of traditional touches that trend-averse socialites find irresistible.

Kate's advent is timely nonetheless. Her unflagging graciousness, guileless manner and nonthreatening good looks are viewed by admirers as a tonic, the sparkling antidote to excess. "There's nothing trashy or vulgar about her," said Anna Wintour, the editor of Vogue, which has featured the duchess several times. "She dresses her age and never looks out of place."

Catherine is, in Mr. Burstell's term, a bracing antithesis to the strident style and manner of many Hollywood celebrities, who "look so phony by comparison," he said. Few would call Catherine adventurous, or even especially chic. She speaks to a conservative mind-set conspicuous on the runways of late. And she also appeals to people's inner Cinderella. There are plenty of designers who will cater to their fantasies, parading frocks with princess seaming, and maybe even a saucy hat or two.

"That fairy tale aspect of fashion is what appeals to Americans," Ms. Zoe said. "Who doesn't want to see the storybook come alive?"

The New York Times