What makes a great partnership? Onstage couples talk about that X factor.

While legendary couples like Bogie and Bacall, and Tracy and Hepburn have torched the screen for years with that ineffable "X" factor, otherwise known as chemistry, the world of dance also can be counted on to seduce audiences with steamy pairings. The perfect partnership can help make or break a performance, and, in the process, elevate a work of art from the mundane to the magical.

The ideal pairing involves years of practice and togetherness in addition to trust, empathy, and the ability to instinctively react in fire moment. It also helps when, as in some cases, the personal and the professional relationship are one and the same.

Take Irina Dvorovenko and Maxim Beloserkovsky, principals with American Ballet Theatre who've known each other since 1984, when they were 10- and 11-year-old students at Kiev's School of Dance (see cover story, Feb. 2001). On the fast track to ballet superstardom, the pair began dating in 1992 while dancing together at the Bolshoi; they married in 1993. The proud parents of a one-year-old girl, the Dvorovenko-Beloserkovsky coupling has received kudos in works that include Romeo and Juliet and Giselle.

Beloserkovsky recalls seeing Makarova and Baryshnikov dance the latter when he was a teenager. "It was a feeling that I was watching a movie. It looked so effortless and went beyond physical contact. It was like two people that know each other forever and sang this song together. It was one voice."

Some people say Dvorovenko and Beloserkovsky, who dance in the grand Russian style but can also tear up the floor in Tharp's Known by Heart, have the same type of chemistry. And what creates that song together? "It's when partners complement each other without overdoing it," he says, "the ability to listen to each other without saying actual words, the ability to read the mind, read the eyes." Dvorovenko agrees. "In duets, rule number one is to listen and be patient," she says. "We never fight, but talk until each feels comfortable."

Another couple that speaks volumes through their passionate performances is Lorna Feijoo and Nelson Madrigal. Married 8 years, together 10, the Gubans studied at Havana's National Ballet School. Principals with Boston Ballet since 2003, they've danced, among others classics, The Sleeping Beauty. "I love dancing with Nelson because he knows my body," says Feijoo. "I don't need to tell him anything because he's going to do whatever I want. There is a lot of trust."

Madrigal, a year younger, says his wife makes him "want to do more, and, when you learn the partnering together, it doesn't matter what ballets you're doing. It's about relationships."

Spanish-born Lucia Lacarra, a principal with Munich Ballet, has been partnered with fellow principal Gyril Pierre, in work and in life since dancing together in Roland Petit's National Ballet of Marseille 11 years ago. "It was love at the first rehearsal," Lacarra confesses. "We have a similar way of seeing ballet. When you know very well the person you're dancing with, you can play with your emotions deeply. I trust him with my life," she adds. "That gives me the freedom to let go completely. Knowing how that person reacts, like two people are breathing at the same time--it is a complete connection, a fusion between the two bodies."

Pierre says that onstage he is aware of Lacarra's every move. "I know what she's going to do by seeing in her eyes or her breathing what emotion she has, and I'm able to react at the right moment."

Although not married--to each other--the Maia Wilkins-Willy Shives pairing operates similarly. When this Joffrey Ballet duo is onstage, they appear bathed in radiance. Says Wilkins, who is married to fellow Joffrey dancer Michael Levine but has been partnered with Shives for eight years, "There's a tremendous freedom dancing with Willy. You never feel afraid. The risks, including trying something new, are worth it. We read off each other, and that can be spontaneous and completely different each performance."

Shives says there is always a story between them, no matter if it's a Nutcracker or something abstract. "Our partnership has grown because it's a work-in-progress where we constantly want more from each other."

While ballet, with its traditional formalism, may sizzle with sexy pas-de-deux, modern dance also boasts a number of great and enduring partnerships. Merce Cunningham recalls dancing with both Carolyn Brown and Viola Farber when he founded the company in 1953.

"We were all new at the game, shall we say, in working things out," he says. "Both of them were so articulate and had wonderful rhythmic gifts. They could see what movement was, and do it in a way that made dance sense to themselves, and not something I just devised for them. There was a give and take between us to allow not only their ability as dancers but what they were as a person to come through. You couldn't force it in any way, but you could show them what you had in your head and find a way to do the particular movement that then became a duet. In both cases it was lucky for me. Carolyn stayed 20 years, Viola 10. Working with them brought up things which we figured out how to do, in one way or another, and it always was a pleasure."

Contact improvisational guru Steve Paxton, who danced with Cunningham and later developed a solo career, has collaborated with fellow improviser Lisa Nelson since 1978. Paxton attributes much of their success to allowing each other freedom. "During duets we have real interest in following each other's inventions, like an ongoing conversation that continually presents surprising felicities. We don't bore or irritate each other."

Adds Nelson, "We recognized a confidence, desire, and commitment to delve into the unmapped territory of improvisational dance, which, for me, combines the art of observation with the craft of memory. Dancing with Steve is dancing with memory incarnate."

Also collaborating since 1978 are Art Bridgman and Myrna Packer, a married couple. Packer recalls an immediate connection. "When we first danced and created work together we felt we brought out the best in each other. That has continued to deepen, because one thing we're able to do is portray an intimacy that comes from the subtleties and innuendos that happen between us."

Bridgman likens their familiarity to being two parts of the same organism. "It's as if we're stepping into something almost preordained for us," he says, "something greater than the sum of its parts."

Indeed, the artistry of two dancers moving in magnificent harmony is a joy for the performers and audience alike. Thrilling, powerful, and eternally enchanting, the perfect pas de deux will continue to capture hearts, infusing, perhaps, a little bit of romance into our workaday worlds in the process.

Victoria Looseleaf is a freelance arts journalist and contributor to Los Angeles Times, Reuters, and La Opinion.