It has been about six years in the making, but American Ballet Theatre’s Michele Wiles and David Hallberg have finally proclaimed themselves a viable partnership, as evidenced by their performance in “Swan Lake” on Friday night. Since joining ABT in 1998, Ms. Wiles’s progress in classical roles has been spotty; her best performances have been in other areas of the repertory. Almost from the day Mr. Hallberg arrived in 2001, the two have been paired together, but until now he hasn’t been strong or experienced enough to give her the support she needed. And to make matters less propitious, Ms. Wiles and Mr. Hallberg often made debuts together.

They have had mixed success with “Swan Lake.” Their New York debut in the production in 2004 was promising, but their performance last year was a wash. The role of the White Swan highlights the weakest areas of Ms. Wiles’s dance articulation, and last year her back and arabesque were too pinched for her to be able to get any traction on the role. But her dancing has been reconstituted since last fall: Her arabesque, her extension, and her jump all bear evidence of remedial tune up. Her high developees on Friday night during her lakeside variation were a real triumph. Although the White Swan suits Ms. Wiles better temperamentally, the technicality of the Black Swan role is a better fit for her than the sustained lyricism of the lakeside scenes. But Ms. Wiles had one wipeout moment during her Black Swan variation on Friday. She fell flat to the floor out of a second position turn, but was on her feet in a second and continued her performance without any visible setback in skill or confidence.

Although Mr. Hallberg has always carried himself with princely aplomb, a narcissistic edge often made his acting in these roles vague and recessive. He didn’t seem to have much to give to a ballerina. But as Prince Siegfried on Friday night, he was believable when he stood with his arms thrown open at the end of the first lakeside scene to show us he had surrendered his heart to Odette. Plunged into the maelstrom of betrayal and loss in the second two scenes of the ballet, he let himself become overwhelmed by events. On Friday, there finally seemed to be a genuine reciprocity of emotion between him and Ms. Wiles. If they can continue to build on what they produced Friday night, they will indeed be a real partnership.

On Thursday night, Nina Ananiashvili danced the roles of Odette and Odile opposite Angel Corella as Siegfried. While nothing in the dual role defeated the ballerina, some of it certainly taxed her. Her technique is still sound, but the White Swan role has always been more difficult for her by virtue of the quality of movement required. In the White Swan adagio, she knit together various impulses. She tried to make her lines as clean as possible, put a third dimension of legato substance into her movement, and vented a powerful emotion that wouldn’t violate classical equilibrium. And in the final phrases of the adagio, everything came together for her.

But the solo that followed was heavy going. She simplified some of the standard choreography and contributed some of her own. In the Black Swan adagio, she was under less duress and all was smooth sailing for her from then on.

Though Mr. Corella’s acting has been much better this season, his dancing has been erratic. On Thursday night, however, everything about his performance was in prime condition. Mr. Corella made the entire first scene a portrait of Prince Siegfried’s melancholy and dissatisfaction. A vaguely Oedipal tension between him and Maria Bystrova, his young and beautiful Queen Mother, added complications to this first act. In the ballroom scene, Mr. Corella’s solo seemed like an expression of his excitement at meeting Odile rather than simply the excitement of dancing before an audience.

In the final lakeside scene, he greeted Ms. Ananiashvili’s distraught Odette with a humble bow that registered as a sincere expression of repentance. When Ms. Ananiashvili made an agitated flight out of his arms, he struggled to restrain her but remained in the right key of balletic dignity. There were lots of dicey supported pirouettes throughout the ballet — perhaps due to Ms. Ananiashvili’s impulsiveness — but this didn’t really detract from the overall performance. In fact, it added an element of danger that suited the twists and turns and reversals of the plot.