To many, "open marriage" is a phrase so laden with 1970s nostalgia that the idea can't be considered without imagining its practitioners leering at each other across shag-carpeted conversation pits, their chest hair spilling out of maroon polyester leisure suits.
While many of today's adherents are aging swingers from the old school, a new generation -- well organized and committed to legitimizing a lifestyle -- continues to push traditional notions of marital fidelity by having sex with people other than their spouses.
But do marriages -- fragile institutions traditionally built on the fidelity and sexual intimacy of two people -- work when the doors of the bedroom are thrown wide open?
"That's like asking if monogamy works," Deborah Anapol, a psychologist and author of "Polyamory: The New Love Without Limits" told ABC NEWS.com. "Sometimes it does, and sometimes it doesn't. It depends almost entirely on the people involved and their willingness to tell the truth and do the work."
"Polyamory," which literally means "many loves" is a new name for an old practice.
"There were a few studies on open marriage in the early '60s and '70s, but the phenomenon seemed to die out and it was just called cheating after that," said William Doherty, a professor of sociology at the University of Minnesota.
"It resurfaced as polyamory, and some groups have imbued it with a spiritual side. They see it as a pathway to personal development. They see it as a high road; it's not cheating, it's growing their relationship," he said.
In 1972, George and Nena O'Neill published "Open Marriage: Love Without Limits," the first book to define the practice and counsel couples on how to grow their own relationships by creating friendships and sexual relationships with other people.
Ten years later, acclaimed journalist Gay Talese would publish "Thy Neighbor's Wife," an experiential look at American sexual mores between the sexual revolution and the AIDS epidemic.
In the book, Talese describes operating a massage parlor in New York City, attending nudist camps and having an extramarital affair.
Though Talese told ABC NEWS.com that his 50-year marriage to his wife, book editor Nan Talese, was not open, the popularity of "Thy Neighbor's Wife" led many Americans to re-evaluate long held ideas about sexual morality, obscenity and fidelity.
It is difficult to determine just how many married people are involved in open marriages. A study from the 1980s suggested it could be as many as 6 percent of all couples, but most experts believe that number is excessively high.
"At least 95 percent of married and cohabitating Americans expect sexual exclusivity," said Judy Treas, a sociology professor at the University of California at Irvine.
As for the success of open marriages, "there have been no scientific evaluations of how well open marriages work," Treas said. "The jury is still out."
Despite the small niche, there is a thriving industry built around the polyamorous. Self-help books, specialized marriage counselors, and retreats, which include everything from courses in Eastern philosophy to the chance to hook up with strangers, are targeted at people in open marriages.