This thesis examines the earliest science fiction dramas on the BBC, broadcast during the period between 1936 and 1955 when the BBC had the monopoly on television within Britain. These dramas were not originally identified as "science fiction", although their fantastic nature was recognised and provided early television writers and producers the opportunity to engage with social concerns and to experiment with the formal possibilities of the new medium. As the American term "science fiction" became more familiar in Britain after the war, the approaches and responses to these productions changed as the audience responded to the connotations of the genre as well as to the individual programmes, and the BBC had to consider these probable responses with regard to its programming. This coincided with the expansion of the television audience, and the increased possibility of a rival television broadcaster being established. These factors required close consideration with regard to the way that the BBC handled genre on television if it was to successfully adapt to these changing circumstances The dangers of making wrong choices with regard to genre were demonstrated by the controversy surrounding Nineteen Eighty-Four (1954), which connected with concerns over loss of British culture. The benefits of making the right choices regarding genre were shown by the success of Tile Quatermass Experiment (1953). Science fiction production expanded across the BBC, continuing to engage with social concerns, but also helping the BBC to develop a particular identity for its television service based on past successes as it prepared for the arrival of its competitor.