This article considers differences between the representation of mutation in science fiction films from the 1950s and the present, and identifies distinctive changes over this time period, both in relation to the narrative causes of genetic disruption and in the aesthetics of its visual display. Discerning an increasingly abject quality to science fiction mutations from the 1970s onwards-as a progressive tendency to view the physically opened body, one that has a seemingly fluid interior-exterior reversal, or one that is almost beyond recognition as humanoid-the article connects a propensity for disgust to the corresponding socio-cultural and political zeitgeist. Specifically, it suggests that such imagery is tied to a more expansive 'structure of feeling', proposed by Raymond Williams and emergent since the 1970s, but gathering momentum in later decades, that reflects an 'opening up' of society in all its visual, socio-cultural and political configurations. Expressly, it parallels a change from a repressive, patriarchal society that constructed medicine as infallible and male doctors as omnipotent to one that is generally more liberated, transparent and equitable. Engaging theoretically with the concept of a 'structure of feeling', and critically with scientific, cinematic and cultural discourses, two post-1970s' 'mutation' films, The Fly (1986) and District 9 (2009), are considered in relation to their pre-1970s' predecessors, and their aesthetics related to the perceptions and articulations of the medical profession at their respective historic moments, locating such instances within a broader medico-political canvas.