The 60-year-old actor, whose sandy-blond hair and boyish good looks made him a household name in the Me decade, was found to have chronic myelogenous leukemia, a type of blood-borne cancer. He's undergoing treatment in the Los Angeles area and his prognosis looks good, says his agent, Dede Binder.
"It's treatable. It's not life threatening at all. He's doing great," Binder says.
Binder wouldn't elaborate about what kind of treatment O'Neal is pursuing, but normal treatment options include radiation, chemotherapy or a bone marrow transplant.
The actor had finished work on the film People I Know, starring Al Pacino, when he learned he had the disease.
O'Neal got his Hollywood start as the hunky star of the '60s prime-time soap Peyton Place before making the jump to the big screen with his Oscar-nominated turn as the handsome jock who falls for Ali MacGraw in Love Story.
The sappy romance about two star-crossed lovers who meet, marry and struggle through the trials of cancer, was a massive hit. O'Neal followed it up with starring roles in Peter Bogdanovich's 1972 comedy What's Up Doc? opposite Barbra Streisand and 1973's Paper Moon, in which the actor was upstaged by his own daughter, Tatum O'Neal, who won an Oscar for her supporting role in the film.
Notable flops soon followed, including Stanley Kubrick's love-it-or-hate-it period drama Barry Lyndon and the epic war film A Bridge Too Far with Dirk Bogarde and Sean Connery.
By the '80s, with his drawing power on the wane, O'Neal was better known for romancing Farrah Fawcett than for his films, which included Irreconcilable Differences (1984) with a young Drew Barrymore and Chances Are (1989), costarring Cybill Shepherd and Robert Downey Jr..
O'Neal and Fawcett called it quits in 1997. Though they never married, they had a son, Redmond, who's now a teenager.
Myelogenous leukemia strikes about 7,000 victims each year in the United States. The disease produces abnormal white blood cells in the bone marrow which eventually push out healthy cells and turn the marrow into diseased fibrous tissue. Those interested on getting more information about leukemia can go to leukemia-lymphoma.org.