The performance of "Giselle" by American Ballet Theatre at the Kennedy Center Opera House last night was so unexpectedly extraordinary from so many standpoints, it's hard to decide what to praise first -- the transcendent portrayal of Albrecht by Mikhail Baryshnikov, dancing once again on a plane that seems to elevate him above all other practitioners of the art; the ascent of ballerina Marianna Tcherkassky to a new level of artistic mastery in her account of the title role; or Baryshnikov's rehabilitation of this warhorse of a ballet, which had been in the brink of stagnation in the ABT repertory, into the profoundly romantic tragedy it was meant to be.

"Giselle" has had three full-blown productions since the founding of ABT, of which the most recent was the late David Blair's in 1968 -- for its time, a splendid effort. Baryshnikov has been at pains to insist that his present refurbishing is not a wholesale restaging of the work, but only an initial "healing" treatment. In fact, though, considerable aspects of the dramatic action, the choreography, the mime, the music and even the decor have been revised, to a sufficient extent to reshape the entire conception of the ballet.

Clearly much remains to be done, and some of Baryshnikov's restorations, especially in Act I, have yet to take hold in performance. Still, a lot of what had become mechanical, slipshod or coarse in the "Giselles" of recent years has now been swept aside, and the company is performing the ballet with a welcome sense of refreshment; once again the whole cast, not just the principals, is dancing as if it cared.

Two things stand out about Baryshnikov's intentions -- a desire to renew the dramatic integrity of the ballet, based on stylistic refinements from his Kirov heritage; and as a corollary, the suppression of athletic virtuosity for its own sale. In contrast to other recent reworkings of classic ballets, this one now has more mime than it did before, with the result that the story is clearer, the acting more credible, the effect more touching.

Books could be written about Baryshnikov's own intricate and sublimely sensitive characterization of Albrecht, but in a way what was most memorable about last night was his effort to scale down the pyrotechnics and to force the technique to serve expressive ends alone. It was as if he were saying: If you, the audience, really want to show your appreciation of what I'm trying to do, then DO NOT yell Bravo! here just because I leaped into the air; don't break the delicate dramatic thread with bellowing. Of course, he didn't entirely succeed; the yelling erupted, inevitably, after his thrilling solo in the Act II pas de deux. But he wouldn't let it throw him off course -- refusing bows, he kept to his wearied, pitiable closing pose on bended knee until conductor Stewart Kershaw led the orchestra into the next sequence.

Tcherkassky rose to her partner's example, with a performance that must count as the finest we've seen from her. She's always been a dancer of exceptional taste, but as Giselle last night, especially in the other-worldly manifestations of Act II, with its supreme technical challenges, she showed us genuinely new heights of achievement, both in the fragile melancholy of her lyrical passages and in the brilliance of her filigreed allegro.

Much more of the performance deserves congratulation than can be adequately covered here -- Magali Messac's serenely implacable Myrta, Victor Barbee's substantially fleshed out Hilarion, Georgina Parkinson's interesting version of Bathilde, Ruth Mayer's sympathetic Berthe, and the charmingly crisp dancing of Rebecca Wright and Warren Conover in the newly amended Peasant Pas de Deux, among many other things. In short, a memorable evening at the ballet.