This episode contains some very powerful scenes as the crew of the Eagle sent to investigate are subjected to a test for genetic purity by a manic Morris
(Anthony McKay, DWB, 1992)
There are some disturbing scenes, particularly the death of crewman Lowry and a mute dwarf. Joan Collins guest stars as Kara, but is her usual unremarkable self. Nevertheless, the episode is a classic.
(Richard Houldsworth, TV Zone, 1992)
Superb effects give this episode immense scale, backed by a clever, exciting script with a number of genuinely shocking sequences. A+
(Chris Bentley, SFX 20, 1996)
Though many other science fiction works have concerned the interstellar space ark, rarely has the idea been presented in such realistic and grotesque terms as this splendidly realised 1999 adventure.
(John Kenneth Muir, Exploring Space: 1999, p76)
Collins and the somewhate gruesome subject matter help this one stand out from the pack. **- (average)
(James O'Neill, Sci-Fi On Tape, p271, 1997)
Mission of The Darians is a perfectly realised epic episode. It is the theme of the downfall of an advanced race due to failures of technology. It shows that the future lies ultimately with the people themselves, not with their technological achievements, and as such this episode embodies what is perhaps the greatest overall concept of the series. 10/10
(Bob Wood, The Future Is Fantastic, 2001)
Space 1999 always did dark well, and this story is one of the darkest. 3/5
(Alasdair Stuart, SciFiNow #10, 2007)