This was the first Cyberman story since Revenge of the Cybermen (1975), as producer John Nathan-Turner wanted to bring back an old enemy, but resisted using the Daleks. Before the title was changed to Earthshock, Nathan-Turner was adamant about keeping the return of the Cybermen a secret. He instructed Eric Saward not to have any reference to the Cybermen in the story's title. Nathan-Turner even had the studio observation galleries closed for the duration of recording and turned down an offer from Radio Times to provide advance publicity of the Cybermen on their cover. The success of this convinced Nathan-Turner to continue to mine the series' past continuity for ideas and old enemies.
Winner of the Doctor Who magazine best Story in their Season Poll.
Costume designer Dinah Collin was assigned the task of bringing the Cybermen into the '80s, and worked on the project with Richard Gregory of effects firm Imagineering. They decided to abandon the rubber diving suits which had previously been the basis of the Cyberman outfit, opting instead of the more high-tech look of army G-suits. At John Nathan-Turner's suggestion, the jaws of the updated Cybermen were left clear so that the actors' mouths could be seen. The producer felt that this would reinforce the notion that the Cybermen had once been human. In a similar vein, Collin and Gregory considered leaving the Cybermen's hands bare - as had been the case in their first appearance in The Tenth Planet - and then seamlessly integrating the flesh with the Cyberman's "metallic" arm. However, it was ultimately decided that this effect would be too complex to achieve. Collin also wanted to do away with the "handlebars" on the sides of the Cyberman helmets, but this was vetoed by Nathan-Turner and Eric Saward, who felt that they were an essential part of the Cyberman image.
The Troopers' laser beams were digitally altered in the DVD release to look more effective.
This story replaced a script called The Enemy Within by Christopher Priest. That story idea dealt with the 'secret' of what actually powered the TARDIS, in this case fear. Somewhere hidden inside the TARDIS was the one being the Doctor feared above all others, and the psychic tension between the two of them produced the energy to move through space and time. The story involved The Doctor having to confront and ultimately defeat this fear and was designed to write out the character of Adric. This was deemed unusable.