Quarry died at Twin Cities Hospital in Templeton in central California. He was admitted yesterday with pneumonia but his niece, Sheri Coolbagh, said that had been brought on by dementia pugilistica, which is brain damage caused by blows to the head.
The progressive malady, similar to Alzheimer's disease, left Quarry virtually helpless and in the care of his family. "He died of complications to pneumonia - brought on by dementia," Coolbagh said from the hospital.
She added that Quarry had suffered for 14 years from dementia that had greatly worsened in the past three years. Almost to the end, she said, he was able to recognise his family and even talk about his fights, and was surrounded by nieces and nephews, sons and daughter, brothers and sisters and his mother.
Quarry, a Los Angeles native who lived with relatives in Paso Robles, fought 66 times, winning 53 of them and 33 by knockout and was cynically promoted as a "great white hope."
He won his first 20 bouts before losing a 10-round decision to Eddie Machen in 1966. Quarry bounced back to win his next 10 fights, twice defeating the former champion Floyd Patterson in 1967.
After Ali was stripped of the World Boxing Association crown, Quarry lost a disputed 15-round title bout to Jimmy Ellis on 27 April, 1968. Fourteen months later, he had another opportunity to win the belt, but was knocked out by Joe Frazier in the seventh round in New York.
On 26 October, 1970, Quarry was Ali's first opponent after his three- and-a-half-year exile and proved easy pickings. Ali knocked him out in the third round on his road back to the championship and sent him to the canvas again in the seventh round on 27 June, 1972.
Obituary; Review, page 6