The Shakespeare Theatre Company’s “Measure for Measure” comes with a parental warning. (Washington Post Illustration)

The poster for the Shakespeare Theatre Company’s new “Measure for Measure” is a bit of a shocker. Glance at it and you’ll find yourself peeking up the garments of a young nun. She’s sitting on the floor. Her face is lifted toward heaven. So are her knees.

“This is not your grandmother’s ‘Measure for Measure,’” STC Chief Marketing Officer Michael Porto says.

Just to be sure that potential ticket buyers know what they’re in for with director Jonathan Munby’s adult-themed staging of Shakespeare’s classic, a warning — in red letters, no less — is posted on the troupe’s Web site.

“Recommended for ages 18 and above,” it says, “but may be suitable for mature audiences, 16 and above. Contains partial nudity, violent and adult situations.”

Sex and violence on the stage are as old as the Greeks, whose tragedies and comedies could be extremely bloody (eye-gouging, anyone?) and remarkably bawdy (see the sex strike in the antiwar “Lysistrata”). For centuries, theaters were often regarded as immoral and profane — dens of vice to be censored and sometimes shut down.

Promotional photo for “Measure for Measure.” (courtesy of the Shakespeare Theatre Company)

Modern theaters are hardly prudish, of course, even when dealing in classics. Lately Washington has eyed an all-nude “Macbeth” by WSC Avant Bard and a memorably violent “King Lear” at the STC, courtesy of Chicago’s Goodman Theatre.

But in the age of the virtual box office, it’s increasingly common for theaters to proactively post a heads-up whenever adult content drapes itself across the wicked stage.

“The benefit of the Web is that you can provide ticket buyers with more information than ever,” says Kennedy Center spokesman John Dow. Movie trailers viewed on cellphones, performance teasers Googled online: these are still-fresh ways that the public interfaces with art before buying a ticket.

“They expect more information than ever because it’s so easily available,” Dow notes.

Porto echoes that. “It’s become something the public is demanding,” he says.

“Measure for Measure” is categorized as one of Shakespeare’s comedies, but its dark plot about a holier-than-thou deputy trying to compromise the virginity of a novice nun makes it one of the Bard’s most troubling plays. Most of the envelope-pushing passages in Munby’s production will occur during a pre-show cabaret set in 1930s Vienna, Porto explains.

“It’s actually a fairly traditional production,” Porto says, even though the guideline is for audiences old enough to vote. “It’s more a matter of setting the tone in a specific way. And like a movie, if there’s one scene where there are naked parts, then the whole thing gets rated that way.”

Last year’s imported “Les Liaisons Dangereuses” at the STC, directed by John Malkovich and featuring a young French cast, came with a red-letter warning about “nudity and explicit situations.” The upcoming “Mies Julie” — a South African adaptation of August Strindberg’s 1888 “Miss Julie,” about a deadly cross-class seduction — is also red-lettered for its “strong adult themes and nudity.” It will be suitable, the STC gauges, for patrons who are at least 16.

But there is no theatrical equivalent of the Motion Picture Association of America, Hollywood’s longtime ratings clearinghouse. Not surprisingly, approaches to advisories are far from standardized.

At the Kennedy Center, age guidelines for coming theatrical attractions are pegged at practically every conceivable threshold: age 6 for “The Lion King,” 8 for “Elf the Musical,” 9 for “Sister Act,” 10 for “Peter and the Starcatcher,” and 13 for “Flashdance – the Musical.” That selection doesn’t include shows specifically for young audiences, which comes with its own “ratings” challenges.

Guidelines for touring shows are provided by the producing companies, Dow says. For “Book of Mormon,” a recent hit at the Kennedy Center that continues on Broadway and on tour, no minimum age is suggested for its ebullient profanities. Instead, the company posts a simple warning: “explicit language.”

Locally, a number of troupes steer clear of age recommendations. Instead, Arena Stage, Woolly Mammoth and Studio Theatre typically offer contextual warnings – “mature language,” “strong themes,” “nudity,” as needed.

A mature audience “is sort of the assumption here,” says Deeksha Gaur, Woolly’s director of marketing and public relations.

Advisories thus can be pretty laid back. “Please note,” goes a message on the page for Woolly’s current offering, Lisa D’Amour’s Pulitzer finalist drama “Detroit.” “The seating configuration for ‘Detroit’ varies significantly from our standard house.”

That doesn’t mean Woolly won’t warn audiences about content. Gaur says the staff is always prepared to guide patrons, and they intervene when it looks like a ticket buyer and a show might be a bad match.

Last week, a family showed up with two girls who looked to be no more than 12 for “Detroit,” a drama that includes mature language and adult themes (sexual situations, copious drinking, lurking addiction). A staffer explained this to the family.

“That’s totally fine,” came the response. “We’re from France.”

“They stayed to the end,” Gaur adds.

At Studio, a mother and her 9-year-old were among the biggest fans of the famously randy “The Rocky Horror Show” this summer. They saw it five times.

“They loved it,” says Beth Hauptle, Studio’s director of marketing and communications. “They posted on Facebook and wrote to us how much they loved the show.”

You won’t see anything about simulated sex on Studio’s page for its current revival of Harvey Fierstein’s “Torch Song Trilogy,” the 1981 play that was a landmark for its compassion and ferocity as the gay pride movement began to bloom. Hauptle says that “performance reminders” — e-mails sent out to anyone who buys tickets — convey whatever warnings may be necessary, from strobe lights and haze to adult content.

Recommending an appropriate age, though, isn’t Studio’s thing. “We just feel you can’t make those judgments for parents,” Hauptle says.

Porto’s motto is preparation; nobody wants to surprise and anger patrons. He spent a number of years with theaters out west, and recalls working for an Arizona troupe producing the troubled-teens-learning-about-sex musical “Spring Awakening.”

“We spent nine months preparing the market for what ‘Spring Awakening’ was going to bring,” he says.

Even so, it’s not every show that needs an advisory or an age marker, especially at a classical theater like the STC.

“We only do it when we feel we need to do it,” Porto says. ‘‘ ‘Importance of Being Earnest’? Not so much.”

Measure for Measure

by William Shakespeare. Through Oct. 27 at the Lansburgh Theatre 450 7th St. NW. Call 202-547-1122 or visit