Last month at Wolf Trap, Washingtonians were treated to a visit by Leningrad's Kirov Ballet, the second oldest classical dance troupe in the world. This week, at the Kennedy Center Opera House, we're getting the oldest -- the Paris Opera Ballet. And one of the ironies of fate is that the Paris troupe is now headed by Rudolf Nureyev, who was the reigning star of the Kirov until he defected from that company 25 years ago. Another is that Nureyev chose to make his celebrated "leap to freedom" at xr the conclusion xr of a Kirov touring engagement -- in Paris.

Until a few weeks ago when it arrived at New York's Metropolitan Opera House, the Paris Opera Ballet hadn't been seen in this country since 1948. The company has an illustrious history, to say the least. But almost all the highlights -- the codification of ballet technique; the premieres of "La Sylphide," "Giselle," and "Coppelia," among other masterworks; the showcasing of such legendary dancers as Vestris, Talgioni, Grisi and Elssler -- belong to the preceding two centuries. In modern times Paris Opera Ballet has languished more or less in the background of international ballet, producing some noteworthy dancers, but very few artistic landmarks of other kinds.

All this has changed radically within recent years. A brilliant new generation of French-born, Paris Opera Ballet-trained dancers has emerged. An influx of choreography from abroad, and particularly from America, has helped revitalize the repertory. The company's reputation has burgeoned accordingly.

It's no accident, of course, that the company's renaissance has pretty much coincided with Nureyev's tenure as artistic director, which began in 1983, even though he acknowledges that his contributions haven't been the only factor in the turnaround.

Assuredly, though, Nureyev has had a lot to do with it. Today, at 48, he remains one of the hottest box-office draws. He looks back on a dancing career virtually without parallel. Since his arrival in the West, he has galvanized and revolutionized ballet wherever his many roamings have taken him. With his virtuosity, restless intellect and exotic personal magnetism, he rehabilitated the image of the male ballet dancer in our time. By osmosis from him, the whole art took on a mass popularity and chic veneer it had known but seldom in the past.

Nureyev isn't shy about ascribing much of Paris Opera Ballet's new dance image to the power of his own example. "If you search your memory," he says, "you'll find that whenever I've danced with companies over a period of time -- the Royal Ballet, the Australian Ballet, the National Ballet of Canada, London Festival Ballet, and yes, American Ballet Theatre -- in each case the dancers have profited from my presence."

This is borne out by the record. Even in cases where resentment was generated by Nureyev's appropriation of so many leading parts and performance opportunities, his box-office magic has afforded some companies a degree of exposure unthinkable without him, and this alone has improved the level of the dancing.

Nureyev has partnered nearly every famous ballerina of the Western world, from Margot Fonteyn, whose career was reborn in the process, to Gelsey Kirkland. He has danced with more companies, in more ballets, more times, than anyone ever. He has extended his creative activities from dancing to the staging of ballet classics to original choreography, and lately to directing one of the world's leading companies. He's been seen on stage, film and television. He was the first dancer to have earned the appellation "superstar" and though his physical powers have waned, his stellar glow seems undimmed.

All this Nureyev brought with him when he took on the directorship of Paris Opera Ballet. But characteristically, he also came with a head full of ideas, and putting them into action has been a large part of the company's recent face-lifting.

"The most important thing was to make a coherent, comprehensive repertoire," he said last week in a telephone interview. "And within this, the first priority was restoring the classics. The company has not had much in the way of classical repertory in a long time. Many people don't realize this, but the company did not have its first 'Swan Lake' until 1960 a production by the Soviet choreographer Vladimir Bourmeister . 'Giselle' was returned to the repertory also relatively recently. For the most part the repertory consisted of ballets by Serge Lifar, Roland Petit and Maurice Bejart."

Nureyev set about remedying this by maintaining or reviving older productions of some classical staples, and adding a number of his own productions, including the "Swan Lake" (1985) that will be seen all week at Kennedy Center.

"I mounted 'Don Quixote,' 'Nutcracker,' 'La Bayadere, Act III,' and parts of 'Raymonda' -- this coming season I'll be doing the 'Raymonda' complete. I also brought in works from America, by Balanchine, Antony Tudor, Paul Taylor and others. I have also gone to younger choreographers, some Americans like William Forsythe who works mainly abroad , Karole Armitage and Lucinda Childs, and some Europeans too, like Nils Christe from the Netherlands.

"I've also tried to promote new French choreographers, but it has been hard -- there are complex problems with unions. Still, I had Francine Lancelot, who has a small troupe specializing in 18th-century dance, do a historical piece for us, and next season Maguy Marin, a young French choreographer, will make a ballet for the company."

Other projects Nureyev has planned for the '86-87 season include his own new staging of Prokofiev's "Cinderella" (though he was loath to talk about his approach to the ballet: "The conception? I'm not going to tell you -- it's a state secret"); two ballets by Jerome Robbins, "In Memory Of . . . ," and "In G Major"; and other ballets new to the repertory by van Dantzig, Neumeier and Ashton.

Temperamental by nature and rebellious in inclination since his Kirov days, Nureyev has had some rough times coming to terms with the thorniest, most politicized ballet bureaucracy in the West -- that of Paris Opera Ballet. There have been periodic reports of backstage and public tantrums, feuds and even physical outbursts.

Nureyev alluded to some of his difficulties in talking about working with foreign choreographers. "The company has such a very complicated administration, and it's so large -- more than 150 dancers 85 in the tour group -- that it can be overwhelming for outside choreographers who come to work with us. I'm trying to streamline the thing so they don't feel overpowered by this enormous machine."

Nevertheless, he insists that his years of staging productions with other companies have armed him for the managerial sides of his post. "I've done all this when I was travelling around staging my ballets in Milan, Vienna, London, so many places. It takes administrative skill to organize productions, to cast ballets, to rehearse them and so on, and I believe I've mastered such matters."

Nureyev also credits the Paris Opera Ballet school in the upbringing of the company's current, much-admired contingent of dancers. "Claude Bessy former Paris Opera Ballet ballerina who directed the company from 1970 to 1972 and now directs its school does an excellent job with the school. I frankly haven't had the time to get much involved with it, but I have made some suggestions -- introducing Martha Graham technique, on a limited scale; initiating some work in historical dance; and classes in Bournonville technique and style -- I think such things are essential to any potential dancer or choreographer."

At the Metropolitan in New York, where the company had two weeks, the programs included two repertory bills containing works by Lancelot, Lifar, Petipa, Balanchine ("Le Palais de Cristal," created in 1947 for Paris Opera Ballet and shortly afterward staged for New York City Ballet as "Symphony in C"), and Nureyev (his controversial "Washington Square," to music by Ives), as well as "Swan Lake."

Unfortunately, logistics (according to Kennedy Center) allowed for staging only "Swan Lake" in the single week locally. On the other hand, Washington must count itself lucky to be the only other city beside New York to see the troupe at all on this visit. Moreover, though we won't be sampling the repertory in any depth, the company will display four casts of principals, as well as many alternates in subordinate roles, during its seven performances of "Swan Lake" -- a testimonial in itself to the troupe's present strength.

(Incidentally, this is quite a "Swan Lake" year. Since the start of 1986, in Washington alone we've seen versions by the Houston Ballet, the Central Ballet of China, American Ballet Theatre (Act II), and the Kirov -- and now comes Paris Opera Ballet. Meanwhile, elsewhere, the New York City Ballet recently staged a new version with all the swans dressed in black except for Odette, in white; and in San Francisco, La Scala Ballet has danced the Franco Zeffirelli production with separate ballerinas portraying Odette (Oriella Dorella) and Odile (Carla Fracci) and both of them dressed neither in black or white, but blue!).

Typically for Nureyev, his "Swan Lake" both pays homage to tradition and departs from it with contemporary, psychological inflections.

"I felt the overall structure of the ballet, Petipa's big ensembles, the big waltzes, the major classical dances, had to be preserved," says Nureyev. "But I also wanted the plot to seem more convincing to a modern audience. Prince Siegfried, the hero, is a romantic, who dreams of an unattainable ideal. But it's a dream, not a reality; so he doesn't go to the forest to look for it, his imagination invents it." In this dream interpretation, the Prince's tutor, Wolfgang, and the evil spirit Von Rothbart, are identified with each other, and portrayed by one dancer (Nureyev himself will dance both Siegfried and the Tutor-Von Rothbart roles in the course of the week).

"I had this idea that a young man like Siegfried would be overpowered by his tutor, as well as by the knowledge he receives from him. So, in his dream, the tutor becomes a diabolical figure. So, also, when he betrays Odette in the dream, he's betraying his own ideal, his own dream, and his life is shattered."