CBS Radio Mystery Theater (aka Radio Mystery Theater and Mystery Theater) was an ambitious and sustained attempt during the 1970s to revive the great drama of old-time radio. The series was created by Himan Brown, a radio legend due to his work on Inner Sanctum Mysteries and other shows dating back to the 1930s.
On CBS affiliates, the series began its long run January 6, 1974. The final episode was broadcast on December 31, 1982. The program aired nightly and ran for one hour, including news and commercials. Typically, a week consisted of three to four new episodes, with the remainder of the week filled out with reruns. There were a total of 1399 original episodes. The total number of broadcasts, including reruns, was 2969.
The format was similar to that of classic old time radio shows such as The Mysterious Traveler and The Whistler, in that a host (E.G. Marshall) introduces each episode and provides pithy wisdom throughout, but unlike the hosts of earlier programs, Marshall is fully mortal, merely someone whose heightened insight and erudition plunge the listener into the world of the macabre.
The show began with the ominous sound of a creaking crypt door, slowly opening to invite listeners in for the evening's adventure, accompanied by Marshall's disturbing utterance, "Come in. Welcome. I am E.G. Marshall." At the end of each show, the door would swing shut, followed by Marshall's classic sign off, "Until next time, pleasant... dreams?," segueing into the show's haunting woodwind theme music.
Marshall hosted the program every year but the final one, when actress Tammy Grimes took over, maintaining the format.
Brown was already one of the leading names in old time radio, having co-created such popular shows as Inner Sanctum Mysteries and The Adventures of Nero Wolfe.
CBSRMT was broadcast each weeknight, with three or four episodes being new originals, and the remainder were reruns. There were 1,399 original episodes broadcast. The total number of broadcasts, including reruns, was 2,969. Each episode was allotted a full hour of airtime, but after commercials and news, episodes typically ran for about 40 minutes.
The format was similar to that of classic old time radio shows such as The Mysterious Traveler and The Whistler, in that there is a host, E.G. Marshall, who introduced each episode and provided pithy wisdom throughout. But unlike the hosts of many classic radios shows, who often had extra-human abilities, Marshall is fully mortal, merely someone whose heightened insight and erudition assist in plunging the listener into the world of the macabre.
The program was pitched, at least initially, to an audience old enough to remember classic radio. Young characters tended to have names more popular a generation earlier, such as Jack, George, Phyllis and Mary. Many scripts, especially those by Ian Martin, showed a tin ear for 1970s youth slang ("Don't let her give you no run-around, dad!" - "The Ghost Plane"; "I think bein' around here's gonna be kicks!" - "Don't Let It Choke You").
But the debut of CBSRMT coincided with America's intense 1950s nostalgia of the mid-1970s. Because radio mystery drama was reminiscent of that era, the program quickly developed a fan base among young listeners as well.
Old time radio expert John Dunning  argues the weakest element of CBSRMT was the scripts, which he argued could vary widely in quality and concept. Dunning thought many of the scripts would have been interesting as 30 minute segments, but lost some impact when expanded for an hour long program; and additionally that many episodes seemed written by scribes unfamiliar with the unique needs of radio drama.
Each show began with the sound of a creaking door slowly opening to invite listeners in for the evening's adventure. Three descending notes from the double basses would introduce Marshall's sinister intonation of, "Come in... Welcome." A muted trumpet sting and timpani roll, then: "I'm E.G. Marshall." A low, eerie woodwind theme would follow as Marshall introduced the program. At the end of each show, Marshall would deliver his classic signoff, "... inviting you to return to our Mystery Theater for another adventure in the macabre. Until next time, pleasant ... dreams?" The door would then creak and slam shut, followed by the woodwinds of the show's haunting theme music.
Marshall hosted the program from January, 1974, until February, 1982, when actress Tammy Grimes took over for the series' last season, maintaining the format.