He was 70.
McDowall died at 7:30 a.m. at his Studio City home, said Dennis Osborne, who said he had cared for the actor in his final months.
``I was at his side,'' he said. ``It was very peaceful. It was just as he wanted it. It was exactly the way he planned.''
No services or interment were planned. McDowall's body was to be cremated by The Neptune Society, Osborne said. He was survived by his sister, Virginia McDowall of Los Angeles, Osborne said.
McDowall was diagnosed with cancer in April and ``he fought it until August,'' when he was declared incurable, Osborne said.
The actor had ``undifferentiated'' cancer, meaning it was not confined to a particular area of his body, Osborne said.
After appearing in several British films, McDowall at 11 was among the children evacuated to the United States during the German bombardment. Hollywood producers were impressed with his innocent face and precise diction, and he was first cast in Fritz Lang's "Man Hunt." The boy emerged as a star in John Ford's saga of Welsh coal miners, "How Green Was My Valley."
"The youngster may prove this studio's boy counterpart to Shirley Temple," Variety magazine said in a 1941 review.
"I can't say I was unhappy as a child actor in films, because I wasn't," he said in a 1963 interview. "I had a particularly wonderful time. The only trouble was that by the time I got to be 17 or 18, Hollywood was still thinking of me in terms of what I had delivered at the age of 11."
Despite his fears, McDowall remained one of the busiest actors in films and television. His most successful film was the 1968 "Planet of the Apes," and he appeared in the ape makeup in three sequels.
His ability to move into almost any role led him to be cast as a Roman emperor in "Cleopatra," a Bible figure in "The Greatest Story Ever Told" and as Cornelius in "The Planet of the Apes" and sequels.
He was born Roderick Andrew Anthony Jude McDowall on Sept. 17, 1928, in London. His father was Scottish, his mother Irish. Educated at St. Joseph's school, he made his film debut at 8 in "Murder in the Family." He came to the United States after the Blitz, the German bombardment of London, began in 1940.
McDowall, who never married, was an accomplished photographer who produced five coffee-table books, starting with "Double Exposure" in 1966. He photographed his lifelong friend and costar of "Lassie Come Home," Elizabeth Taylor, in a nude layout for Playboy magazine in 1963. A longtime student of film, he gathered one of the largest private collections of old movies.
By BOB THOMAS