For a choreographer whose ballets have often dealt -- sometimes in graphic detail -- with morbid lust, mayhem and psychological torment, Sir Kenneth MacMillan seems singularly mild and collected in person. He speaks quietly and without gesture, reclining his husky figure against a hotel room sofa, a picture of dignified British reticence. Only his soft, poodle eyes hint at acquaintance with melancholy.

He retains his tranquility and his diffident smile even while he discusses painful episodes in his career. One such concerned his ballet "Romeo and Juliet," originally created for England's Royal Ballet and just now restaged by MacMillan for American Ballet Theatre, which will present the first American production at the Kennedy Center Opera House tomorrow night.

In 1965 the inaugural cast of the Royal Ballet, first at Covent Garden and then a few months later at the Metropolitan Opera House, featured Margot Fonteyn as Juliet and Rudolph Nureyev -- the Soviet defector who was then at the height of his powers and popularity -- as Romeo. The casting wasn't MacMillan's choice, and therein hangs a tale, given newly abrasive edge recently with the publication of memoirs by British ballerina Lynn Seymour, highly prized by MacMillan for her surpassing dramatic flair.

"You want, of course, to know what 'really' happened," says the choreographer in a self-mocking tone. "I actually made the whole ballet on Seymour and Christopher Gable. The general administrator of Covent Garden at the time was Sir David Webster, and he'd arranged for an American tour directly after the London premiere with Sol Hurok. Hurok was not only a very powerful, very important impresario -- he was also extremely important to the fortunes of the Royal Ballet. For Hurok there were no two ways about it -- it had to be Fonteyn and Nureyev, who were the stars of the day, and that was that. I was many years younger, and I simply wasn't able to stand up to that kind of pressure.

"As I recall, there were to be six alternate casts of principals, and Seymour and Gable were scheduled to be last. But due to injuries to other dancers, they actually got to do it the second night. And though Margot and Rudolph were quite marvelous in their own ways, it was really Seymour and Gable who came off best in those parts."

Of the many versions of Prokofiev's celebrated ballet score, MacMillan's is the one most frequently seen and widely admired in the western world (the Soviet version of 1946 by Leonid Lavrovsky, for the Bolshoi Ballet, has the status of legend in Russia). Beside Fonteyn and Seymour, such ballerinas as Antoinette Sibley, Natalia Makarova and Gelsey Kirkland have been among the notable Juliets. The Romeos have included Anthony Dowell, David Wall and Mikhail Baryshnikov, who danced it as a guest artist with the Royal Ballet in 1975, and also performed the Balcony Scene in the 1977 film "The Turning Point," partnering Leslie Browne, who will be ABT's first Juliet (with Robert La Fosse as her Romeo) tomorrow night. Baryshnikov's estimate of MacMillan is reflected in his naming him to the post of artistic associate of ABT last fall, completing an administrative triumvirate for the company that also includes the new associate director, John Taras.

"Romeo and Juliet" won a new order of fame for the Royal and MacMillan, who directed the English troupe from 1970 to 1977 and remains now its "principal choreographer." It also helped to establish MacMillan as a world-class master of narrative form and classical tradition. His latter-day reputation as a daring innovator within that tradition, however, and as "the poet of passion, of dark, unhappy desires and frustrations" as one English writer put it, has rested as much on the turbulent, sometimes controversial series of dramatic ballets MacMillan created in the '70s, starting with "Anastasia" and going on to "Manon," "Mayerling" and "Isadora."

There are other sides to MacMillan's work, as the crisp neoclassicism of "Concerto" and the frolicsome, ragtime-accompanied "Elite Syncopations" demonstrate. But even "Romeo and Juliet" embroiled him in choreographic controversy, at least within ballet circles, where some maintained that MacMillan's version of the Shakespeare-Prokofiev staple was suspiciously derivative of John Cranko's Stuttgart production of 1962 -- shown at the Kennedy Center in its first American staging by the Joffrey Ballet only three weeks ago.

"There's been a lot of talk of me 'borrowing' from Cranko's production," MacMillan says. "The truth of the matter is that we both borrowed from the Lavrovsky version, which made such an impact on us when Ulanova danced it in London. John and I were very great friends Cranko died at 45 in 1973 , and we saw the Bolshoi production together. What did strike me particularly about John's version when I saw it in Stuttgart was this -- with the Bolshoi, the feuding families, the Montagues and the Capulets, seemed almost royal. The scale of Cranko's ballet gave a much more intimate view of them, and after all, these weren't royal families, just rather rich and powerful ones. Certainly nowhere have I taken any choreography from John's version. If there's any similarity, it's in this sense of intimacy.

"Cranko had used a pillow dance in the ball scene the men tote cushions in a grand promenade, drop them to the floor, and fall to their knees on them before the women at the end following Lavrovsky. I didn't do this, because it seemed to me it made the men look very subservient to the women. But I think the drama is about a patriarchal society, and in my ballet these roles are reversed -- it's the women who are subservient. I also felt such a reversal would make Juliet's rebelliousness seem all the more striking, poising herself against her elders the way she did."

MacMillan also had the Shakespearean text in mind constantly as he choreographed. "I couldn't literally interpret each line," he says, "but for some lines I tried to find equivalent dance imagery. It doesn't matter at all if the audience recognizes any of that, it was just a working strategy of mine. In any case, it's extremely hard, when you're dealing with a writer like Shakespeare, to find images as potent as the words."

MacMillan would like to see Baryshnikov in the ABT "Romeo and Juliet," and not just as the hero, but realizes it may take some time as the dancer gets himself back into shape from his recent stint of movie-making, and recovers fully from old injuries.

"I hope Misha will return to dancing soon, so I can choreograph new ballets for him," MacMillan says. "He's one of the world's great dancers still, and it's a shame we don't get to see him. First, I think, we'll be trying to get him back into 'Romeo and Juliet,' I hope perhaps at the Met next spring. He was a brilliant, very vibrant Romeo in London, a very individual approach he had. But I'd also love to see him do Mercutio, and he's said that he'd like to."

MacMillan says that in rehearsing "Romeo and Juliet" with the ABT casts he took the tack of a theatrical director, as he does with all his narrative ballets, asking for more realistic, actors' reactions, in contrast to the stylized, cliche'd responses more habitual with ballet dancers. He's directed plays, by Ionesco and Strindberg, for instance, for English theater companies. He hasn't directed a movie -- though he says he'd love to -- but he's worked on several, including "The Turning Point" and Herbert Ross' "Nijinsky," for which he choreographed several major scenes.

But it was the movies -- and American musical movies in particular -- that lured him into the dance profession in the first place. "There was no background in my family," he says of his early years in his native Scotland. "And my father wasn't too keen on the idea. It was the movies that did it -- Astaire, of course. I wanted to be a tap dancer. So I went and took tap lessons, and one day -- I was about 14 -- my teacher said, 'What about ballet?' 'What about ballet?' I replied -- I had no idea ballet was something boys did. So she started me in classes, and I began to read about Nijinsky and all that, and became madly interested. And then I was hooked."

The tap dance aspirations have stayed with MacMillan, and come in handy every so often. Last summer, for example, he created a tap routine for a British TV production of Kurt Weill's "The Seven Deadly Sins." And he confesses to being a closet tapper still. "My assistant, Monica Parker, also loves tapping," he says. "Sometimes, backstage, when nobody's looking, we get into a corner and have a little tap."