AMERICAN Ballet Theatre is ending its annual winter series at the Kennedy Center Opera House. But somehow it seems as if it's been here four months rather than four weeks because the period has been so eventful and rife with change, both for good and ill.

The biggest change, of course, has been the one at the top, and with the start of Mikhail Baryshnikov's tenure as artistic director, we've become more conscious than ever that ABT is the only ABT we've got -- that is to say, that it's the only ballet company in this country large enough in scale and resources, and broad enough in its base and legacy, to serve as America's "living museum" of the art.

Baryshnikov has already demonstrated a profound regard for this singularity of function and destiny. The returns are far from complete, certainly since his directorship has scarcely begun and he's had to contend with some severe initial handicaps -- aside from managerial problems and various crises involving principal dancers, a flu epidemic coupled to the "normal" (for ballet) quotient of injuries has disabled a considerable fraction of the company for much of the Kennedy Center run.

Nevertheless, it looks very much as if Baryshnikov is going to bring to him company leadership the same swift intelligence, reverence for tradition, insistence on stylistic integrity, and a very "American" taste for risk and adventure, that have been among his chief marks of distinction as a dancer. If his initiatives can be carried even to partial fruition, the company itself, its audiences and ballet in general will all be beneficiaries.

Three major thrusts are discernible in what we've seen over the past month. The first is an attempt to amplify, bolster and refine the company's classical heritage. Some of this must come from Baryshnikov's own sense of himself, what he represents in history, and what he is best fitted to convey to future generations. There's no question here of his trying to turn ABT into an American Kirov Ballet. But he is striving to impart to the troupe the best of what he himself took from Leningrad in the way of stylistic finesse and its basis in the 19th-century classical repertory. The new "Raymonda" divertissements, the "Pas d'Esclave" from "Le Corsaire," and Baryshnikov's provisional remodelings of "Les Sylphides" and "Giselle" are steps in this direction, and we know from announced plans for the rest of the season that more are surely to come. If the results thus far are uneven, that was to be expected. But one important hurdle has been passed -- a rejuvenation of the dancers' attitudes towards the "classics," which ABT had been on the verge of taking for granted as mechanical box-office obligations.

The second, and most conspicuous, theme of the series was generous apportioning of roles to dancers within all ranks of the troupe. The tactic has many significant reverberations. It tells the company that Baryshnikov is serious in his respect for the high level of aritstry that prevails in ABT, and that he means to foster the development of its individually talented dancers in the one way that counts -- by giving them chances to perform substantial parts. It gives a sense of refreshment to the repertory that can only come from the idiosyncratic contributions of gifted interpreters. tAnd it says to the public -- here Baryshnikov seems to be banking on the growth in sophistication that has been noted in Washington and elsewhere -- that ballet is not about superstardom or circus tricks, but about fine dancing, distinguished ensemble and the edifying rewards of versatile repertory tradition.

The third guiding principle was the preservation of ABT's own worthy past. Besides the new and refurbished classical items, the programs here also saw the addition of Balanchine's "Prodigal Song" and Ashton's "Rendezvous" to the repertory, along with the first local showing of Natalia Makarova's staging of "La Bayadere," all of this very much within the historic ABT framework; revivals of ;Twyla Tharp's "Push Comes to Shove" and Jose Limon's "The Moor's Pavane," both from choreographers oriented towards "modern dance," complemented four ABT staples: Balanchine's "Theme and Variations," Robbins' "Interplay," De Mille's "Rodeo," and Baryshnikov's "Nutcracker" -- a healthy mix by any measure. Not yet visible in this Washington season was anything in the way of the newly choreographed work to which Baryshnikov has declared a firm commitment, but this clearly takes the kind of time and latitude he hasn't yet had at his disposal.

The firing of Gelsey Kirkland and Patrick Bissell -- tragic, but apparently unavoidable -- along with the absence in Washington of Makarova, Anthony Dowell (who's only signed on thus far for four performances of "Bayadere" on the current tour) and Fernando Bujones left a considerable vacuum at the head of the company's roster. The compensation, at this level, was Baryshnikov's own consummate performances throughout the run. He danced in five ballets -- his first "Les Sylphides" in the West, plus "Giselle," "Prodigal Son," "Push Comes to Shove" and "Nutcracker" -- leaving a humbling awe in his wake in each instance. There were moments in each of these ballets when his dancing seemed beyond the pale of human limitation, moments of such intensity and poetic consonance that it hurt to watch, even when, as in a luminous second in "Sylphides," all he was doing was stretching to his toes, wreathing his arms above him, and tilting his melancholy countenance to an earthward gaze (if you can call this "all").

Otherwise, though there was nothing about the season one would call "spectacular," there was much that was revelatory. Magali Messac, a new principal, showed us a lovely sense of style, at once proud and reserved.Marianna Tcherkassky added new layers of elegance and dramatic presence to her already accomplished dancing. Alexander Godunov toned down the extravagance of his manners and uncovered far more authority than we'd seen in earlier performances. Susan Jaffe, the 18-year-old corps de ballet dancer thrown into the spotlight in "Pas d'Esclave," was one of a number of newly discovered or emerging talents among the company's lower echelons. Among others were Cheryl Yeager, whose "Sylphides" suggested an ample classical future; Robert La Fosse, who took an assortment of majoy assignments in full strude; and Ronald Perry, whose stately, musical composure in "Theme and Variations" was large with promise. And any number of other dancers disclosed either further artistic progress or hitherto unsuspected aptitudes or both, a list that surely includes Kristine Elliott, Johan Renvall, Cynthia Harvey, Ruth Mayer, Victor Barbee, Gregory Osborne and Lisa de Ribere.

It was the same company as of old, but a new company, after all, as well.