When it comes to men's suits, says influential New York City tailor Thom Browne, the skinny leg is in. Designers like Dolce & Gabbana and Ralph Lauren are waving goodbye to the slouchy, oversized look; it's hello to pencil-thin suits straight out of a 1960s movie. Even at mass-market retail stores like H&M and Gap, the new style for spring is narrow jeans cropped at the ankle. The move toward the straight and narrow was launched in large part by Browne, 38, who favors what he calls the Congressman suit—the lean look favored by John Kennedy when he was a junior Senator. Browne's $2,800 suits feature skinny flat-front trousers with boxy jackets. "The pants are so tiny they're essentially leggings," says Michael Macko, director of men's fashion-buying at Saks Fifth Avenue. Says Browne of his style: "It's an early-'60s Brooks Brothers sensibility mixed with bespoke. Men's clothing has been stuck in the mud for such a long time, I wanted to offer something very different."