When the curtain goes up on American Ballet Theatre’s opening night gala this evening, one dancer in particular will be relishing the spotlight. Just two weeks ago, David Hallberg, 24, learned that he would be promoted from soloist to principal dancer – and his promotion is effective tonight.The tall, blond Mr.Hallberg will perform the pas de deux and coda from Sir Frederick Ashton’s “Sylvia” with his frequent partner, Michele Wiles, marking the beginning of a demanding and promising season.

For Mr. Hallberg to have reached this rank at this time is particularly remarkable. ABT’s current roster of male dancers is extremely talented, and the competition for the top roles is formidable. But Mr. Hallberg brings an uncommon regal flair to the stage.As a soloist, he danced the role of Espada in “Don Quixote” with enough dash and seduction to rival any real-life bullfighter.

In person, however, his majestic, noble character gives way to youthful cheer. At 6 feet 2 inches, he’s slender, with a narrow face and wavy,light blond hair. In overalls, he would look like a Midwestern farmboy. When he arrived for our interview,he was sweaty from rehearsal and unshaven. The fuzz on his chin looked pubescent. Even so, he had the charm and alertness of someone who knows this is his moment.This season, as a principal, he will perform leading roles in “Sylvia,” “Swan Lake,” “Cinderella,” and “Le Corsaire.”

Born in South Dakota, Mr. Hallberg began his classical ballet training at age 13, in Phoenix, Ariz. At 12, he was a soldier in a local production of “The Nutcracker,” and that’s what hooked him. “I was in the first act, and every night I would beg my mom to let me stay so I could watch the second act,” he said. “I would stand in the wings completely mesmerized.”

Though the beauty of the form attracted his eye, he soon discovered how much work goes into dancing: “I found out, once I started training, that it was so demanding, so difficult, because nothing is ever perfect. So I became attracted to the rigor of it.”

Mr. Hallberg first came to ABT for one of its summer courses. After he graduated from high school in 1999, he studied for a year at the Paris Opera Ballet School. “It was very humbling,” he explained.”They were very French.”

Not only was the atmosphere strict, there was limited possibility for advancement.Because most of the company’s dancers are French, he said, “They made it very clear to me when I arrived that I had no chance of getting into the company.”

Fortunately, he had a standing offer from Kevin McKenzie, ABT’s artistic director, to come back to and join the Studio Company – ABT’s second company. Less than a year later, he joined the main company as a member of the corps. He was appointed a soloist in 2004, and this season, he dances as a principal.

The news of his promotion came when ABT was on tour in California. Instead of a private meeting, as is customary, he found out in front of the whole company. “Usually Kevin has a private meeting with you first,”Mr.Hallberg explained. “It’s climactic, but it’s anticlimactic, because you can’t share it with anyone until it’s announced to the company, which is usually a couple of days later.”

But things were different this time around. “In California, they didn’t have time to have a meeting because I was so busy with performances. Kevin just decided to surprise me in the meeting with all the dancers, and I was shocked.”

Although Mr. Hallberg is usually cast in lyrical roles, he’s still in an introspective phase of his career. “The feedback I get is that I’m a very lyrical, poetic dancer; more fluid, princely,” he said. “But there are other aspects of dance that excite me, more contemporary repertoire. And the bravura roles are fun, too. Bravura meaning like Don Quixote – more Spanish, with more flair,” he explained.

The competition for those roles, however, is fierce: “We have a lot of great Latins in the company that do that very well.”

Mr. Hallberg paused and reflected before making sure his interest in those roles got on the record. “But just because things don’t come so easily, that doesn’t mean that you shouldn’t try them,” he said. “It’s kind of like an opera singer. Like Deborah Voigt is known for Wagner and Strauss, and Renee Fleming is more known for Handel, but that doesn’t mean that they don’t venture out into other repertoire.”

Like most natural performers, Mr. Hallberg isn’t shy about enjoying his major life moments in front of an audience. Recently, he has found a new way of reaching that audience. Since April, he has been contributing to the blog TheWinger.com. Started by New York City Ballet dancer, Kristin Sloan, the blog follows the life of a dancer in pictures and posts.

When Mr. Hallberg read about The Winger, he sent an e-mail to Ms. Sloan complimenting her creativity. She invited him to contribute so that the site could have perspectives from both of the city’s major ballet companies. But more importantly, these two careers summarize all the emotional highs and physical lows that compose a dancer’s life. Ms. Sloan’s posts have become a diary of physical therapy appointments, as she continues to struggle with hip problems that almost ended her career three years ago. Mr. Hallberg’s posts have been a record of his successes – his promotion, a profile in W Magazine, a mention in Time Out.

Having experienced mostly the highs lately, Mr. Hallberg is, understandably, full of confidence, but his enthusiasm is refreshingly candid and unaffected. The dancer lives by himself, in an apartment in the 70s on the West Side, a neighborhood popular with dancers because of its proximity to Lincoln Center and to the dance studio Steps on Broadway. He’s devoted to opera and other arts, as well as one sport: tennis: ” I love, love, love tennis. It’s strategic. It’s planned.Roger Federer has an amazing game of finding out his opponent’s weaknesses and playing off of that.”

In a city where many young people pride themselves on their ability to stretch the limits of both their social and their professional lives, dancers inhabit a separate universe. In sleeping, eating, and everything else, discipline must rule. “Most of us don’t go through that party phase,” Mr. Hallberg said. “And we never go through that college, fraternity, beer-guzzling phase. Tonight, I’m celebrating my birthday a little bit, but I have to weigh in that tomorrow I have a full run of Cinderella, which is very, very hard, so I can’t be out all night drinking.”

This self-restraint at this point is automatic: “Discipline is instilled at a very young age for us – most of the time, 10 or 11 – so this is kind of what we know, it’s second nature to us.”

When I checked back with him a few days later, he said that in the end he didn’t go out on his birthday, to save himself for Cinderella, but the next night he had dinner with a group of friends on the Lower East Side.

Tonight, on the Upper West Side, Mr. Hallberg’s discipline and drive will no doubt be apparent. At 24, this principal dancer knows this about being a professional: The beers can wait, his audience can’t.