This study explores a new genre of futuristic literature for teenagers. It demonstrates that it has mainly developed along dystopian lines, which, like Nineteen Eighty-Four and Brave New World, extrapolate from present trends to predict horrifyingly credible versions of the future. It considers the features which set a children's dystopian novel apart from these classic 'adult' dystopias, and particularly focuses upon the question of imaginative closure and the ways in which the didacticism is carried in cautionary near-future realism. The work takes a novel approach by exploring writers' imaginative use of evolutionary theory. Chapter 1 demonstrates that the perceived responsibility to point young readers to a better world exerts a powerful influence on the literature produced, making it very difficult to produce a wholly negative, ironic work. Chapter 2 shows, however, that writers have repudiated The Chrysalids' narrative tactics, at least at surface levels. Few depict Wyndham's reading of evolution, which is unequivocally used to envisage the radical improvement of the human species. They attempt instead to introduce ambiguity into the text's presentation of human nature. The following two chapters show that, although children's writers frequently seek to use evolution as a moral metaphor, simultaneously expressing the hope that man can change, and warning against the dire consequences if he does not, the emphasis they have placed upon predictive realism, rather than Wyndham's speculative fantasy, counteracts their effort to articulate hope for a young reader. Huxley, Orwell and Golding all use extinction to carry their warning. A comparison with children's texts reveals that whereas 'adult' dystopian writers present hope indirectly and ironically, children's writers typically supply hope within the text itself. The tendency to present child protagonists as evolutionary agents of heroic transformation in the dystopian context results in the imaginative and ideological fracture which characterises the literature. The premises of the dystopian context make such a hope seem naively unrealistic and simplistically conceived. Chapter 5 documents the few futuristic books in which the expression of moral meaning takes a different literary guise. Man is seen in relation to the environment, rather than embattled against society. The imaginative emphasis is upon speculation, rather than prediction, extensively employing the techniques of fantasy and the marvellous to discover new angles of perception. A Wizard of Earthsea is used to illuminate the tactics of the 'ambiguous utopia', which leaves room not only for the moral evolution of the protagonist, but also allows the best (as well as the worst) in human nature to become credible possibilities. The Conclusion draws together the ways in which children's authors organise their narratives to try to overcome the creative dilemmas of producing dystopian fiction for an immature audience. In particular it highlights the possibilities of a new style of didacticism, which is based upon the notion of empowering the reader as an active, transformational ideologist, rather than a passive recipient of a mandated meaning.