Abstract Asymmetric Norms and the Dual Complexity Spaces One of the recent advances in Computer Science was due to the possibility of establishing a mathematical model that account the distance between algorithms and programs when they are analyzed in terms of their computational complexity (complexity distance), where computational complexity is interpreted in terms of running time, for example. In the last decade, several authors have done a big e_ort in obtaining a robust mathematical theory, which was a useful tool that played, in this context, a similar role that normed linear spaces have played in di_erent scienti_c areas. In the context of Computational Complexity, it is shown that Asymmetric Normed Linear Spaces constitute a very satisfactory model. This thesis is focused in the study of the properties of these spaces, similarly to the classical properties that are studied in the case of normed linear spaces. Thus, we have studied separation properties of asymmetric normed linear spaces, obtaining in particular a characterization of Hausdor_ness; we have obtained a satisfactory theory of bicompletion for these spaces; we have analyzed compactness on _nite dimensional asymmetric normed linear spaces; we have studied conditions under which an asymmetric norm de_ned on an algebraically closed subset of a linear space can be extended to the whole space and we have analyzed the structure of the dual space and the weak topologies associated to it. Finally, we have applied our theory to Computer Science, speci_cally to the so-called Dual Complexity Spaces.