Pernell Roberts, the man who played Adam Cartwright in “Bonanza” and the title character in “Trapper John, M.D.,” has died at 81.

His wife, Eleanor Criswell, told The Los Angeles Times that he passed away from cancer on Sunday.

Roberts starred as the eldest son of the Cartwright family from  ’Bonanza’s’ beginning in 1959.

Despite being part of one of the most popular Westerns to ever hit TV, Roberts left the show six years in after a reported disagreement with the NBC show’s producers.

After making a brief foray into film and theatre,  the small screen pulled Roberts back. In 1979 he joined the cast of “M*A*S*H” spin-off “Trapper John M.D.,” in which he played the title character, Dr. John McIntyre (originally played by Wayne Rogers in the “M*A*S*H” TV series). He was nominated for a best actor Emmy for his efforts.

Roberts stuck with the role for the show’s lifetime, which ended up being seven seasons.

His last appearance was in 2001 in an episode of ‘Diagnosis: Murder’, according to E! Online.

Funeral services were to be held today, the Web site reports.