everly Sills, whose sparkling coloratura soprano and warm, spunky personality made her an international opera celebrity and whose experience as a mother made her a passionate advocate for children with special needs, has died. She was 78.

Ms. Sills died Monday of lung cancer at her home in New York, according to her longtime manager, Edgar Vincent.

Dubbed "America's Queen of Opera" by Time magazine, the Brooklyn, N.Y.-born Ms. Sills, widely known as "Bubbles," was an American success story. She rose to stardom without receiving what was considered mandatory - training in Europe. Moreover, she made her career essentially outside the sacred portals of the Metropolitan Opera in New York paving the way for generations of wholly American-trained singers to succeed without Met certification.

Her repertoire eventually encompassed more than 70 roles, and she recorded 18 full-length operas and several solo recital discs. Her "Manon" received the Edison Award for best operatic album of 1971, and her Victor Herbert album won a Grammy Award in 1978.

Ms. Sills also gave opera a human face through television appearances displaying the optimism, wit and lack of diva temperament that endeared her to general audiences as much as her technically accomplished, emotional and insightful dramatic interpretations won the affection of opera aficionados.

She had a silvery, lyric soprano that she intelligently employed in creating a character, narrowing the sound to evoke a younger woman or widening and deepening it to reflect greater maturity. She sang more than the usual number of coloratura embellishments - including perfect trills - with ease, agility, accuracy and clarity, but always in the service of a role.

Sills needed contact with an audience. She was far more comfortable onstage, where she could amplify her characterizations with subtle facial expressions and physical gestures, than making recordings.

In later years, she was troubled by an increasingly wide vibrato but almost always compensated for any vocal lapses with dramatic insights.

Singing, in fact, was only the first, if longest, part of her career. After she retired from the stage at 50, she spent a decade as an exceptionally capable administrator of New York City Opera, turning around the financially beleaguered company that gave her a career and to which she remained faithful as her reputation soared. Later, she assumed the volunteer post of chairman of Lincoln Center in New York City, which she held from 1994 to 2002, and then accepted the volunteer post of chairman of the Metropolitan Opera. In both positions, she proved a master fundraiser.

Spurred by the births of a daughter who was deaf and a son who was mentally disabled, Ms. Sills also served for many years as chair of the board of the March of Dimes Foundation as well as national chairwoman of the organization's Mothers' March on Birth Defects.

Her rise to fame was not meteoric. She joined New York City Opera in 1955 after repeated unsuccessful auditions that began in 1951. But after making her company debut as Rosalinde in Johann Strauss' "Die Fledermaus," she sang leading roles there over the next 25 years in works by Handel, Bellini, Rossini, Donizetti, Mozart, Offenbach, Thomas and Verdi, as well as modern repertory, including the title role in Douglas Moore's "The Ballad of Baby Doe." She also sang in the U.S. premiere of Luigi Nono's avant-garde "Intolleranza" in 1960 for the Opera Company of Boston.

What Ms. Sills regarded as the turning point of her career came in 1966, when she performed the fiendishly difficult role of Cleopatra in Handel's "Giulio Cesare," opposite bass-baritone Norman Treigle in the title role, to open City Opera' s new home at Lincoln Center.

She wrote in her 1976 autobiography, "Bubbles: A Self-Portrait": "It was — and I don't mean to be immodest, but after all these years I am a pretty good judge of performances — one of the great performances of all time in the opera house."

After that, she confirmed her success, singing the Queen of Shemakha in Rimsky-Korsakov's "Le Coq d'Or," the title roles in Massenet's "Manon" and Donizetti's "Lucia di Lammermoor" and the three heroines in Puccini's "Il Trittico."

Reviewing her "Manon" for the New Yorker in 1969, critic Winthrop Sargeant wrote: "If I were recommending the wonders of New York to a tourist, I would place Beverly Sills at the top of the list — way ahead of such things as the Statue of Liberty and the Empire State Building."

Sills was born Belle Miriam Silverman on May 25, 1929, to Russian Jewish immigrants Sonia and Morris Silverman. She acquired the nickname "Bubbles" because she was born with a bubble in her mouth, and it was as Bubbles Silverman that she debuted on the radio show "Uncle Bob's Rainbow House" as a 3-year-old, the same year that she won a Brooklyn contest as "the most beautiful baby of 1932."

She also appeared on other radio shows, among them "The Major Bowes Capital Family Hour" and "Arthur Godfrey's Talent Scouts."

Sills began her vocal studies at age 7 with Estelle Liebling, who had been Italian soprano Amelita Galli-Curci's voice coach. At 10 she got a part on the radio show "Our Gal Sunday" and also sang on radio commercials for Rinso White detergent. She made her opera debut in 1947 singing Frasquita in Bizet's "Carmen" with the Philadelphia Civic Opera.

When her father, a life-insurance broker, father died of lung cancer that year, Sills began to sing in clubs to make ends meet. From 1951 to 1952, she toured the country with the Charles L. Wagner Opera Company, reportedly singing Violetta in Verdi's "La Traviata" about 40 times and Micaela in "Carmen" more than 60 times. Her first major role in a major company was Helen of Troy in Boito's "Mefistofele" with San Francisco Opera in 1953.

It was on a New York City Opera tour in 1955 that she met Peter Greenough, associate editor of the family-owned Cleveland Plain Dealer, whom she married a year later. The couple had two children: a daughter, Meredith ("Muffy"), who was born deaf in 1959, and Peter Jr. ("Bucky"), born in 1961, who has autism. Greenough had three children from a previous marriage. To tend to her children, Sills began to curtail her professional activities.

With her husband's encouragement, however, she returned to the stage in the mid-'60s, rejoining City Opera for her breakthrough performance as Cleopatra. She went on to debuts in Vienna in 1967 and at London's Covent Garden in 1970. Her 1969 debut at La Scala in Milan, Italy, in Rossini's "The Siege of Corinth," drew rapturous international praise, with Italian audiences dubbing her "La Fenomena" (the Phenomenon).

Long kept out of the Metropolitan Opera because of general manager Rudolf Bing's condescension toward her and City Opera, Sills made her overdue Met debut only after his retirement. Her performance in "The Siege of Corinth" in 1975 earned her an 18-minute ovation. But she sang there only five seasons.

L.A. saw her in the '60s and '70s, when she sang at the Hollywood Bowl and with City Opera at the Dorothy Chandler Pavilion. Winding down her career, she created the title role in Gian-Carlo Menotti's "La Loca" in San Diego in 1979. But by the end of that decade, critics were noting a fall-off in her vocal ability, and she recognized that her work was suffering.

"I've done everything I set out to do," she said at the time, "sung in every opera house I wanted to…. To go on past the point where I should, I think would break my heart. I think my voice has served me very well. I'd like to put it to bed so it would go quietly, with pride."

She made her farewell performance in 1980, sharing the stage with Joan Sutherland in a San Diego Opera production of "Die Fledermaus."

For the next stage of her career, Sills reportedly walked away from nearly $8 million in unsigned contracts to take over City Opera. The company was struggling financially, with $5 million in debt. In 1985, as things were beginning to turn around, the warehouse containing nearly all the company's costumes and scenery burned to the ground.

"There were days when I could hardly talk myself into coming to the office," Sills later told Time magazine. "There would be a big meeting on Tuesday morning, and I would be told there was no money for the Friday payroll."

Still, she was able to reverse the company's fortunes, revamping the production schedule, revitalizing the repertoire with new and unusual works and introducing for the first time in an American opera house the use of supertitles — translations projected on a screen above the stage — which made opera accessible to wider audiences.

By the late '80s, the company had eliminated its deficit and was operating in the black with a $25-million budget. She relinquished her duties in 1989. Looking ahead, she said, "I don't think a young, vital company should be led by a 65-year-old woman."

Five years later, she came out of retirement to become chairman of the Lincoln Center for the Performing Arts, making her the first performing artist to serve on its board. She remained until 2002.

Although she again planned to retire, she was coaxed back to action later that year to become chairman of the Metropolitan Opera, where she worked until 2005. Sills also starred in several operas broadcast on television, including "The Daughter of the Regiment," "The Barber of Seville," "La Traviata" and "Manon." She co-starred with Carol Burnett in a TV special, "Sills and Burnett at the Met," and hosted and appeared on "The Tonight Show" numerous times. She won four Emmys for her interview show, "Lifestyles With Beverly Sills," which ran twice weekly on NBC over a two-year period in the late '70s.

Her awards included the Presidential Medal of Freedom in 1980 and a Kennedy Center Honor in 1985. Her health made news in 1974 when she underwent surgery for a malignancy. But five weeks later she was starring in L.A. in Bellini's "I Puritani." "She sang beautifully," wrote Times music critic Martin Bernheimer, "radiating health and warmth, almost acting as it if were just another night at the opera."

Her husband died last September. She is survived by her two children; two stepdaughters, Lindley Thomasett and Nancy Bliss, both of New York; and one granddaughter, Allyson Bliss.

Services will be private; donations may be made in Sills' name to the Multiple Sclerosis Society, 733 3rd Ave., New York, NY 10017.