Ratings Terror of the Zygons was released on
BBC1 in four weekly parts from 30 August to 20 September 1975. "Part One" was released to an audience of 8.4 million viewers making it the highest viewed episode. It was followed by the lowest viewed, "Part Two", with only 6.1 million. Parts three and four were viewed by 8.2 and 7.2 million viewers respectively. Audience
Appreciation Index were taken for the first and third episodes, they scored ratings of 59 and 54.
Critical reception In
The Television Companion (1998),
David J. Howe and Stephen James Walker wrote that
Terror of the Zygons gave a stereotypical portrayal of the Scottish and showed how much the show had changed since abandoning its regular UNIT premise. They felt that the story gave UNIT its "dignity and believability" and praised the conception of the Zygons, though they noted that the shapeshifting concept was not original. Despite classifying the Skarasen as the "major weakness", they wrote that "the story remains a strong one". In 2010, Mark Braxton of the
Radio Times praised the "exquisitely horrible" design of the Zygons and the cliffhanger of the first episode where a Zygon attacks Sarah. He also was positive towards guest actor John Woodnutt and the incidental music, calling the whole production "a class act", aside from the Loch Ness Monster.
DVD Talk's John Sinnott gave the story four-and-a-half out of five stars, praising the cast and the design of the Zygons. Ian Berriman of
SFX felt that it was "churlish" to criticise the Loch Ness Monster effect when the story "gets so much right, including first-class direction, pitch-perfect performances and a hauntingly eerie, folky score". He also was positive towards the design of the Zygons and their spaceship, though he found their scheme farfetched. Christopher Bahn, reviewing the story for
The A.V. Club, described it as "fun" but noted that it could be formulaic instead of trying to be "ground-breaking"; he criticised the scene in the second episode in which Broton tells Harry everything about the Zygons, which did not leave much surprise for the later episodes. Nevertheless, he praised the cast, the action sequences, and the Zygons, which he described as a "wonderfully surreal triumph of Doctor Who visual design", though otherwise they functioned as a typical
monster-of-the-week. Reviewing the serial in 1999, literary critic
John Kenneth Muir acclaimed
Terror of the Zygons as "a riveting and horrifying adventure", singling out the fleshy Zygon costumes for particular praise. He drew parallels with a number of historic
Doctor Who serials, noting that the Zygon story drew on some familiar
Doctor Who ingredients, including alien invasion (
The Invasion), "body snatchers" (
The Faceless Ones), an oil rig setting (
Fury from the Deep),
biomechanical technology (
The Claws of Axos) and the revelation of an ancient Earth legend to be alien in origin (
The Dæmons). However, he was disparaging of the use of a
glove puppet to represent the Loch Ness Monster, comparing it to "the
Invasion of the Dinosaurs debacle". In 2009, a poll conducted by
Doctor Who Magazine of the 200 stories produced up to that point saw the serial finish in seventeenth place. ==Commercial releases==