McLean Stevenson was born in Illinois, where his father was a cardiologist. After serving in the Navy, he attended Northwestern University, receiving a bachelor`s degree in theater arts. Stevenson worked at a radio station, played a clown on a live television show in Dallas and sold insurance and medical equipment. In 1961, Adlai Stevenson Mclean`s second cousin, invited him to a party, where, mingling with show business luminaries like Gower Champion and Sanford Meisner Stevenson decided to become an actor. He auditioned and won a scholarship to the American Musical and Dramatic Academy. While studying under Meisner and Lee Strasberg. He made his acting debut in a summer stock production of `The Music Man` and followed up with work in television commercials, `The Defenders` and `The Ed Sullivan Show`. He also appeared with Alan Alda in the series `That Was the Week That Was`, for which Stevenson was a writer. He also wrote for `The Smothers Brothers Comedy Hour`. After a guest appearance on `That Girl, ` with Marlo Thomas he was signed to a regular role on `The Doris Day Show` in 1969. In the fall of 1973, Stevenson, already a popular guest on the `Tonight` show, began a long-running second career as a guest host on the show. He appeared in his best known role as the bumbling surgeon and commanding officer, Col. Henry Blake, on the successful TV series `M*A*S*H`. However, Stevenson was soon chafing at his second-banana role on `M*A*S*H` and asked to be released from his contract. In the last episode of the 1974-75 season, Blake was sent home and his plane was shot down over the Sea of Japan. After leaving M*A*S*H, Stevenson headlined in a series of failed TV shows.