The rehearsal breaks at 2:15 p.m. Patricia McBride slips out of the arms of Mikhail Baryshnikov and trudges to her dressing room. "Even after dancing an entire evening," she sighs, "he is hardly even panting!" She reaches for a two-liter bottle of Coke and drinks it, chugalug, to the bottom. If that's breaking training, who cares? At 36, an age when many ballerinas think of hanging up their toe shoes, McBride is pirouetting into superstardom as Baryshnikov's new partner.

Keeping up with ballet's 31-year-old bionic man is not easy. It means at least three hours of rehearsal and up to two hours of performing with the demanding Misha nearly every day. In the six months of their partnership, though, McBride has matched his stamina with intelligence and grace.

When Baryshnikov defected from the American Ballet Theatre last May to join George Balanchine's more innovative New York City Ballet, Patricia McBride was literally waiting in the wings. Balanchine paired them in the flirtatious classic Coppélia, and the critics were enchanted.

Their onstage rapport is obvious, but Baryshnikov, contrary to his usual behavior with dancing partners, has made no move to enlarge their offstage relationship. "He's a very charming man," she says, "but after all, I am a married woman." Her partner responds with a sudden grin. "She is very ugly," he says, leaning over to peck her on the cheek. "She never smiles. It is terrible. Her balance is terrible." McBride ends the exchange: "He has a wonderful sense of humor—I hope."

Patricia Lee McBride was born in 1942 in Teaneck, N.J. Her father, Eugene, left the family when she was barely 3. Her mother, Margaret, went to work as a secretary in a bank to support Pat and her younger brother, Eugene, now a computer programmer. "I never felt really deprived," Pat recalls, "but it was a big deal for me to get a new dress." Even so, her mother managed to pay for ballet lessons. "She thought it would be nice for a little girl." It was, of course, the turning point. By the time she was 12, Pat says, "I made up my mind I wanted to be a dancer"—though she had never seen a professional ballet.

At 14 she was accepted as a scholarship student at the School of American Ballet, the official incubator for City Ballet. At 16 Balanchine chose her for the corps, and at 18 she became the company's youngest principal dancer.

In the 1960s Balanchine teamed her with the athletic Edward Villella, and the combination was magical. "She always had this wit in her dancing," Villella recalls. "She was secure enough in her steps to project a sense of humor."

Neither her partners nor her occasional dates with dentists and the like gave her any romantic notions. ("Most ballets are more interesting than most men," she once remarked.) Then in 1968 Jean-Pierre Bonnefous knocked on the dressing room door. For Pat, the earth trembled. Bonnefous was the beau idéal of the Paris Opera Ballet. He spoke no English; she, no French. She reduced her concert schedule to visit him in Paris. He came to New York to see her. "I never thought about marriage," Jean-Pierre says, "but with Pat there was no other way."

First they broke up, then got back together when he joined the New York City Ballet. They decided to live together and, after three years, made it legal in 1973. Their marriage is an extension of their careers: Dancing is paramount. The prospect of children seems remote. "Pat's not a wife or homemaker," says Jean-Pierre. "She's a dancer, and she's not going to stop."