…so that I don't.

nna, a 22-year-old graduate student in Manhattan, said she remembers clearly how she was introduced to one of New York's sauciest underground social scenes. It was via an instant message from a stranger who had seen her personals ad online at Nerve.com. A local promoter of erotic events called One Leg Up was organizing a party in a TriBeCa loft on the theme of the film "Moulin Rouge," her suitor wrote, and he wanted to know if Anna would be interested in going "with me and my hot tattooed girlfriend." Anna mulled her reply, then fired off an e-mail message.

"I was like, `Yeah, dude, I'll check that out,' " she recalled.

To gain entry, Anna first had to send an erotic essay and a photo of herself to One Leg Up's founder, a husky-voiced, 33-year-old proselytizer for sexual experimentation who goes by the name Palagia. Anna made the cut, was given the party's location and a pass phrase — "untie my corset" — and on a chilly night last year donned fishnet stockings and high heels and headed out to her first sex party.

The gathering was awkward at first, she said, but at 12:30 a.m., a gong rang, signifying that guests should strip to their underwear, and things soon began to heat up. Anna said she spent most of the evening entwined with a couple she had just met — not the one that invited her — and besides the minor annoyance of having to locate all her clothes at the end of the night, she said the experience lived up to her expectations. She has since been to 15 similar parties in Manhattan, and though just a year above the legal drinking age, counts herself a full-fledged member of what insiders refer to simply as "the lifestyle."

Her take on the scene is uncomplicated: "I think sex is cool and people should have a lot of it," she said.

The idea of swinging may evoke an image of middle-aged, ennui-riddled suburban couples of the 1970's — think of key parties and the movie "Bob & Carol & Ted & Alice." But among a certain adventurous younger crowd in Manhattan these days, swinging — or at least a high-velocity form of sexual exploration that resembles swinging, but for the dearth of actual spouses (many participants are shy of marrying age) — is thriving with a twist. Unlike the dismal, failed swinging attempt in "Carnal Knowledge," in which two husbands make a surreptitious deal to seduce each other's wives, the younger scene is driven largely by women — many of them erotic-party promoters who use the Internet as both a marketing tool and a screening aid, to keep their crowds enticingly attractive and to keep paying customers coming back.