Jack Valenti, then President of the Motion Picture Association of America (MPAA), formally announced the commencement of a new Motion Picture Code and Rating Program on November 1, 1968; a mode of industry self-regulation designed to replace the, by then discredited, Production Code. Despite the Program's intended role in providing freedom of choice, censorship has persisted after 1968. Censorship is defined here as the efforts by some to restrict the viewing options of others, for reasons of personal morality, commercial self-interest or ideological necessity. American moviegoers and other consumers of American cinematic culture have, paradoxically, been freed from choice. The availability of 24/7 porn on cable television and the undoubted explosion of explicit violence in mainstream cinema after 1968 are superficial distractions from the homogenising effects of both the pressure to make movies that can be screened to large predominantly teenage audiences and the pressures not to upset vocal pressure groups. In extending and mapping out the territory of the consumer the industry has, both in the types of movie on offer and in the mode of regulation chosen, effectively curtailed the space for the citizen to ask more demanding questions either about movie content or about the benefits of allowing a small number of media conglomerates to construct the viewing menu. The Program remains in place but its efficacy has been widely questioned. The thesis breaks the development of the Program into three phases organised around Richard Heffner's operation of the Program between 1974 and 1994. In the early years, despite the self-styled liberalism of the New Hollywood renaissance, both ideological and commercial constraints were applied to content. Only after Heffner's arrival in 1974 did the Program begin to function as Valenti had originally envisaged. However, the slow emergence of narrowcasting and the expansion of conglomerate ownership ensured the continuance of commercial self-censorship. These changes found maturation in a third phase of the Program's operation, after 1994. The research considers evidence of commercially motivated self-censorship as well as evidence of politically motivated censorship. The cumulative effect of industry change has been a commodification of entertainment- a denial of any interest other than that of the consumer- and the privatisation of a key part of the process of setting cultural norms. The thesis considers the risks for a functioning democracy posed by the emergence of a global entertainment complex that has an overwhelming economic interest in shaping the 'marketplace of ideas'.