NEW YORK — How do you prove you’re a virgin in the town that inspired “Sex and the City”?

The producers of an off-Broadway show are giving away free tickets to anyone who can demonstrate his or her chastity.

Which raises the question: Just how will the theater know?

Producer Ken Davenport, 34, had a hypnotist screen people standing in line on Thursday for the free tickets to the first preview of his 90-minute comedy, “My First Time,” and determine their status. The show opens July 28.

The “virgin” stunt serves the subject of the play, “which is to get people to talk about their first sexual experience, something that almost any person on the planet has in common, whether in the United States or Rome,” Davenport said.

Davenport’s human lie detector, Sebastian Black, describes himself as a mind reader and a psychic hypnotist. “He’s a master of body language and tone of voice,” Davenport said.

About three dozen prospective virgins stood before the 55-year-old hypnotist. He held each one’s hand, probing each face as he asked simple questions about their daily life — then threw a curve ball: “When was your first time?”

Kelly Meneer, a 22-year-old from Ohio who studies acting, walked away a shoo-in.

“He knows my pathetic love life!” she said with a big smile, glancing at a male friend.

Then came the “half-virgin” — as Terry Bedesi described himself.

Explained the 23-year-old bookseller from Queens: “There’s certain parts of me that’s still a virgin.”

A no-go.

The show is based on a decade-old Web site that invites people to anonymously share their stories about losing their virginity.

“I still have the Metallica shirt he wore that night,” one person wrote on the site.

Davenport could not say how many actual virgins were admitted to the theater Thursday.