Pernell Roberts, TV actor

LOS ANGELES - Pernell Roberts, 81, who shocked Hollywood by leaving TV's

Bonanza

at the height of its popularity, then found fame again years later on

Trapper John, M.D.

, died Sunday.

Mr. Roberts, the last surviving member of the classic western's cast, died of cancer at his Malibu home, his wife, Eleanor Criswell, told the Los Angeles Times.

Although he rocketed to fame in 1959 as Adam Cartwright, eldest son of a Nevada ranching family led by Lorne Greene's patriarchal Ben Cartwright, he chafed at the limitations he felt his character was given.

"They told me the four characters [Greene and himself, Dan Blocker, and Michael Landon as his brothers] would be carefully defined and the scripts carefully prepared," he complained to the Associated Press in 1964. "None of it ever happened."

It particularly distressed him that his character, a man in his 30s, had to defer to the wishes of his widowed father.

He agreed to fulfill his six-year contract but refused to extend it, and when he left the series in 1965, his character was eliminated with the explanation that he had moved away.

Bonanza, with its three remaining stars, continued until 1973. Blocker died in 1972, Greene in 1987, Landon in 1991.

In 1979, Mr. Roberts landed another series, Trapper John, M.D., in which he played the title role. The character, but little else, was spun off from the Korean War comedy-drama M-A-S-H. It aired until 1986.

His' other venture into series TV was FBI: The Untold Stories (1991-93), in which he acted as host and narrator.