"In the last few years before my retirement," says dancer Erik Bruhn, "I have to admit I was getting a little impatient with my heroic roles and image - impatient not to leave my old existence, but to move onward, to step into something else."

Now the change has come, and Bruhn is as much a center of attention as ever. Prior to his leave-taking in 1971, due to an enduring, painful illness, the Danish-born artist was known throughout the ballet world as the male classical dancer par excellence. The "retirement" ended in 1975 with an appearance in an American Ballet Theater gala.

Now he's back with ABT, currently in Washington, and doing a variety of less physically demanding character roles instead of the romantic gallants he'd come to personify in the public imagination.

Last night, for instance, he danced his first Petroushka in Washington (he repeats the part tonight), in the company's all-Stravinsky, he'd been seen here partnering Natalia Makarova in a new restoration of Fokine's "Firebird." On Sunday evening, in the program concluding the ABT's three-week run at the Kennedy Center, Bruhn will appear in his own staging of "La Sylphide," not as the romantic protagonist James - a role he made one of the modern glories of classical ballet - but as Madge the Witch, the hideous crone who is James' nemesis.

Part of the reason for the 49-year old Bruhn's enthusiasm for his transformation is his conviction that age is not an artistic liability.

"In America, there is so much emphasis on youth, some dancers think that's all they need - to be young forever. But in Europe, in Denmark where I was raised, there is a long tradition of respect for maturity.

"I remember seeing Youskevitch dance for the first time. He was in his mid-thirties, which nowadays is considered advanced or a dancer, and I remember thinking, when I get to be 35, that's when things will really start for me. But the world's attitudes changed so much, so suddenly, that by the time I reached 35, you couldn't afford to admit it - it felt wrong to be mature.

"The sad thing is that it takes maturity in a dancer to know what to do with the great classic roles, but just when you get there, the body is ready to depart from such roles. I was 19 when I first danced James, and I was a disaster. Oh, I could dance, technically I was brilliant, everybody admitted that. But I was wooden and stilted in the part.

"Fortunately, people have a tendency to leave you alone once you make such a flop. That's when my own thoughts about the role began to develop; I experimented and worked at it on my own and finally came to understand it."

Afterward, Bruhn became a sort of prisoner of his own triumphs. For years he fought the fear of having to go out of stage and each time dance better, act better, be better than - Erik Bruhn. Then the fear began to be accompanied by acute abdominal pain. In December of 1971, at the Kennedy Center, in fact, he danced James again in "La Sylphide" with Carla Fracci - it was to be his last stage appearance for four years. Later he underwent surgery for a perforated ulcer.

That performance, however, was one of the peak experiences that have made the whole show worthwhile for Bruhn. "In those last five years, I had moments, in different countries, different roles, when everything I'd worked for seemed to come together in a single night - as James, as ALbrecht in 'Gisells,' as Jean in 'Miss Julie,' as Don Jose in 'Carmen'. That night in Washington was one of those occasions. I was in great physical distress, and knew I couldn't continue the season. So I felt I had nothing to lose by holding anything back - I was open in so many ways I wouldn't have been under ordinary circumstances."

Bruhn has plunged into the latest phase of his career with a characteristic lack of regret about the past. "I was happy to leave Janes and Albrecht to the younger ones. It was a relief never to have to play the Prince in 'Sleeping Beauty' again - I'd always hate the role. He's just cardboard, there's no way to make him anything but a cavalier. I felt ready to take up another kind of challenge in my life."