Countdown was a weekly comic published by Polystyle from 20th February 1971-25th August 1973, though it changed its tile several times during the course of its 132 issue run, remaining as Countdown (later subtitled Countdown the Space Age Comic from #19-45, Countdown for TV Action from #46-56 and TV Action in Countdown in #57-58) for only 58 issues before becoming TV Action & Countdown with #59 and finally just TV Action with #101. One gimmick associated with the original tile was that the pages were numbered in reverse order, each issue therefore being effectively a "countdown" to the next. Originally printed on high quality glossy paper using the Photogravure technique previously used on the original Eagle with many of the pages in full colour, from issue #59 it began to make economies, moving to a less expensive paper stock. The comic concentrated primarily on strips based on TV shows, notably Doctor Who (featuring the third Doctor), The Persuaders', Dastardly & Muttley, The Secret Service and Gerry Anderson's Thunderbirds, Lady Penelope, Captain Scarlet, Joe 90, Stingray, Zero X, Fireball XL5 and U.F.O, much of the Gerry Anderson related material being reprinted from TV Century 21 (though a new Thunderbirds strip with art by Don Harley began in #44). There was also a totally original science fiction strip, Countdown by John M. Burns. Later additions under the TV Action title (which saw the majority of the Anderson related strips dropped and Doctor Who moved to the front cover) included Hawaii 5-0, Droopy, Tightrope, Motormouse & Autocat, Mission Impossible (by John Burns), Dad's Army by Peter Ford, The Protectors by Jose Ortiz, Cannon by Martin Asbury and Alias Smith & Jones by Colin Andrew. Other creators to work on the title included Gerry Haylock, Frank Langford and Harry Lindfield on Doctor Who, and the title also included (unusually) several non-fiction articles on space exploration, mostly written by Arnold Kingston. Countdown Annual's were published in 1972 and 1973, a Countdown Holiday Special in 1971 and a Countdown With TV Action Holiday Special in 1972. There were also TV Action Annual's in 1973-74 and a TV Action Holiday Special in 1973.
- The Doctor Who strip, which had been imported to Countdown from TV Comic, returned to its original home after TV Action was cancelled.
- In January 2017, Doctor Who Magazine reprinted the Countdown Doctor Who story Sub Zero in Doctor Who Magazine presents Countdown to TV Action: Sub Zero, a free giveaway edition with issue #508.