Anne d’Harnoncourt, 64, who led the Philadelphia Museum of Art for 25 years, died on Sunday at her home in Philadelphia.

She suffered a stroke while recuperating at home after a minor hospital procedure, the Philadelphia Daily News reported.

D’Harnoncourt served as director of the museum since 1982 and as both director and CEO since 1997. Prior to that, she was for 10 years the museum’s curator of 20th-century art.

In a statement, the museum’s chairman, Gerry Lenfest, called her death a severe loss to the museum and to the art world in general. She “was learned, a gifted speaker, had an effervescent personality, was a great director and, above all, a deeply caring person,” Mr. Lenfest said. “We will miss her greatly.”

D’Harnoncourt presided over a period of enormous growth at the museum. In the last 15 years, annual attendance grew to just under a million visitors, from 582,000. The museum drew accolades for its exhibitions, including retrospectives of such artists as Constantin Brancusi, Paul Cézanne, and Salvador Dalí, and surveys on topics from the art of the Pennsylvania Germans to Japanese design.

Last fall, the museum opened a major expansion. It transformed the Ruth and Raymond G. Perelman Building, across from the museum’s main building at the top of Benjamin Franklin Parkway, into new galleries for works on paper, textiles, costume, and design, as well as new space for the library and archives.

D’Harnoncourt led the museum through two major capital campaigns. The most recent, which concluded in 2004, raised more than $246 million.

She also oversaw the reinstallation of all of the European collections and the renovation of the modern and contemporary art galleries.

Born in 1943, d’Harnoncourt grew up in New York, where her father, René d’Harnoncourt, a former Austrian count, was the director of the Museum of Modern Art between 1949 and 1967. She attended the Brearley School, graduated summa cum laude from Harvard University, and got a master’s degree from the Courtauld Institute of Art in London.

She began her career at the Philadelphia Museum of Art in 1967 as a curatorial assistant. From 1969 to 1972, she was an assistant curator at the Art Institute of Chicago. She was a specialist in the art of Marcel Duchamp.

Deeply committed to Philadelphia and the museum, d’Harnoncourt over the years turned down offers to run MoMA and the National Gallery of Art in Washington.

She “became totally associated with the museum and the city — she was a great citizen,” the director of the Metropolitan Museum of Art, Philippe de Montebello, said. “She really was the ideal director,” he said. “She was a scholar. She was an ex-curator. She was public-spirited. She had enormous charm and warmth.” Mr. de Montebello described himself and his colleagues as in shock over the news.

Agnes Gund, who as president of MoMA in the early 1990s tried to lure d’Harnoncourt there, said she “blazed the way” as a female director of a major museum and “handled it with grace and her wisdom and wit.”

Ms. Gund singled out d’Harnoncourt’s close relationships to contemporary artists. “She was very good friends with Jasper [Johns], [Cy] Twombly, and Ellsworth [Kelly], and she got them to loan her things and do things with her that were exceptional,” Ms. Gund said. “Most directors don’t have that intimate connection with artists, and she was very beloved by them.”

Ms. Gund added that d’Harnoncourt and her husband, Joseph Rishel, the Philadelphia Museum’s curator of pre-1900 European paintings, “worked so marvelously together, in a way you wouldn’t imagine it could happen.”

The current director of MoMA, Glenn Lowry, said: “What always impressed me about Anne is how she evolved over time, as politics of running a museum became more complicated. She never bemoaned the changes that took place in the field but saw them as creating opportunities — opening [the museum] up to the community, embracing not just the politics of the city but the spirit of the city.”

The director of the Art Institute of Chicago, James Cuno, also praised d’Harnoncourt’s dedication to the museum’s role in the life of Philadelphia. “She can be credited not only with the resurgence of the museum but also, to a considerable degree, with the resurgence of the city,” Mr. Cuno said in an e-mail message.

She is survived by her husband, Mr. Rishel.