Science fiction films may be viewed as existing as threads within a web, and at the same time constituting the web. The metaphor is apt: texts and contexts and their relationship have a difficult accommodation with each other, an interdependent and dynamic relationship. The text is a thread in the web, as are elements of context, yet the threads are in a symbiotic and constantly changing relationship with each other, as the web is constantly in a state of renewal and change. At the same time, the text itself is a web, as are the various contexts. The threads are both ephemeral and fleeting, while incredibly strong. This thesis is about the polysemy of science fiction film: its subject is the films of the fifties that belong to the genre of science fiction. But the area of study began as an investigation of the science in science fiction films; the way in which films construct that science, the end result of that construction and the totality of the discourse of science in relation to other discourses of power and influence. The investigation of those issues involves a multi-layered investigation into science fiction, in a similar way to Tulloch and Alvarado's approach to the Dr Who television series.1 Approaching science fiction films from a perspective of genre, as in chapter one, uncovers a set of arguments about the science in science fiction, as well as establishing the global nature of some science fiction. These concerns lead into the discussion in chapter two of the social and historical context of the fifties, specifically in the US. Science plays a major role in these contexts, in the sense of the importance of science in creating these contexts (from this perspective) as well as the effects of the application of this science. But the historical and cultural contexts tend to suggest that science fiction films are in large part both a response to the social and historical context, and also create that context. This would not be quite accurate: the production of many science fiction films mobilise other arguments, arguments relating to the industry of Hollywood, and the specific industrial context that gave rise to some very financially successful science fiction films, as well as some films where the budget was good for a few days filming. Science and technology are sometimes important elements in this industrial context as well. Part II traces the nature of science in these films, using the contexts in Part I to anchor the science and its implications and effects. Foregrounded is the debate in which science is both key player and, in many cases, antagonist. The debate is traced and the various representations of science and its nature are tracked and highlighted. Science can cause change, by virtue of its nature of uncovering superstition, but the worth or desirability of that change is open to question. The control of science is a related issue. The thesis examines science at a period that saw the efflorescence of science fiction films. The examination of those films tells us a great deal about the concerns of the time, as well as the science that figures so powerfully in the webs of culture of the fifties.