Roberts (l) appeared in Bonanza for six years before leaving the show
Pernell Roberts, known to millions as Adam Cartwright in TV western series Bonanza, has died at the age of 81.
The actor, who was the last surviving cast member of the long-running series, also portrayed the title role in MASH spin-off Trapper John, MD.
Roberts initially found fame alongside Lorne Greene, Michael Landon and Dan Blocker as the oldest of Bonanza's three Nevada rancher siblings.
But he shocked Hollywood by leaving the show at the height of its popularity.
The series continued without him, eventually becoming - after Gunsmoke - the longest-running TV western in US history.
Blocker and Landon, who played Adam's younger brothers Hoss and Little Joe, died in 1972 and 1991 respectively.
Greene, who played patriarch Ben Cartwright before going on to appear in Battlestar Galactica, passed away in 1987.
Roberts' departure from Bonanza was motivated in part by his disenchantment with his character's subordinate relationship to Greene's.
"Doesn't it seem a bit silly for three adult males to get Father's permission for everything they do?" he once complained.
Following his exit, the actor went on to make guest appearances in such shows as Hawaii Five-O, Mission Impossible and Ironside.
His role in Trapper John, MD saw him portray an older version of MASH's Korean War surgeon, played by Elliot Gould in Robert Altman's film and Wayne Rogers in its TV spin-off.