Even then, Winehouse's performances were sometimes shambolic, and she admitted she was "a terrible drunk."
Increasingly, her personal life began to overshadow her career.
She acknowledged struggling with eating disorders and told a newspaper that she had been diagnosed as manic depressive but refused to take medication. Soon accounts of her erratic behavior, canceled concerts and drink- and drug-fueled nights began to multiply.
Photographs caught her unsteady on her feet or vacant-eyed, and she appeared unhealthily thin, with scabs on her face and marks on her arms.
There were embarrassing videos released to the world on the Internet. One showed an addled Winehouse and Babyshambles singer Pete Doherty playing with newborn mice. Another, for which Winehouse apologized, showed her singing a racist ditty to the tune of a children's song.
Winehouse's managers went to increasingly desperate lengths to keep the wayward star on the straight and narrow. Before a June 2011 concert in Belgrade — the first stop on a planned European comeback tour — her hotel was stripped of booze. It did no good,
Winehouse swayed and slurred her way through barely recognizable songs, as her band played gamely and the audience jeered and booed.
Winehouse flew home. Her management canceled the tour, saying Winehouse would take some time off to recover.
Though she was often reported to be working on new material, fans got tired of waiting for the much-promised followup to "Back to Black."
Occasional bits of recording saw the light of day. Her rendition of The Zutons' "Valerie" was a highlight of producer Mark Ronson's 2007 album "Version," and she recorded the pop classic "It's My Party" for the 2010 Quincy Jones album "Q: Soul Bossa Nostra."
But other recording projects with Ronson, one of the architects of the success of "Back to Black," came to nothing.
She also had run-ins with the law. In April 2008, Winehouse was cautioned by police for assault after she slapped a man during a raucous night out.
The same year she was investigated by police, although not charged, after a tabloid newspaper published a video that appeared to show her smoking crack cocaine.
In 2010, Winehouse pleaded guilty to assaulting a theater manager who asked her to leave a family Christmas show because she'd had too much to drink. She was given a fine and a warning to stay out of trouble by a judge who praised her for trying to clean up her act.
In May 2007 in Miami, she married music industry hanger-on Blake Fielder-Civil, but the honeymoon was brief. That November, Fielder-Civil was arrested for an attack on a pub manager the year before. Fielder-Civil later pleaded guilty to assaulting barman James King and then offering him 200,000 pounds (US$400,000) to keep quiet about it.
Winehouse stood by "my Blake" throughout his trial, often blowing kisses at him from the court's public gallery and wearing a heart-shaped pin labeled "Blake" in her hair at concerts. But British newspapers reported extramarital affairs while Fielder-Civil was behind bars.
They divorced in 2009.
Winehouse's health often appeared fragile. In June 2008 and again in April 2010, she was taken to hospital and treated for injuries after fainting and falling at home.
Her father said she had developed the lung disease emphysema from smoking cigarettes and crack, although her spokeswoman later said Winehouse only had "early signs of what could lead to emphysema."
She left the hospital to perform at Nelson Mandela's 90th birthday concert in Hyde Park in June 2008, and at the Glastonbury festival the next day, where she received a rousing reception but scuffled with a member of the crowd. Then it was back to a London clinic for treatment, continuing the cycle of music, excess and recuperation that marked her career.
Her last public appearance came three days before her death, when she briefly joined her goddaughter, singer Dionne Bromfield, on stage at The Roundhouse in Camden, just around the corner from her home.
Despite the years of frustration and disappointment, Winehouse retained a huge body of fans, all hoping she would find her feet again. Some gathered outside her home after her death, laying flowers, comforting each other and taking in the police tape and ambulance that marked the end of her journey.
Winehouse is survived by her parents and an older brother, Alex. Her father, Mitch, who released a jazz album of his own, was in New York when he heard the news of her death and immediately flew back.
Winehouse's spokesman, Chris Goodman, said "everyone who was involved with Amy is shocked and devastated." He said the family would issue a statement when they were ready.