This thesis describes the expression of focus in Basque declarative sentences through the use of morphological, lexical and syntactic devices. It analyzes the different degrees of emphasis that can be provided by the combination of these three types of mechanisms, and the interaction ofthe expression of focus with the expression of the new/given information distinction.This study shows that constituents containing background information normally occur either before the focused element or after the verb, and that topics occur in sentence initial position. Elements whose information is non-contrastive and whose reference is already included in the verbal inflexion are normally deleted. The element with new information always occurs before the verb and receives the highest semantic prominence. The content of the focused element can also be emphasized by morphological means. This combination of syntactic and morphological mechanisms, along with the fact that there are several places in which each sentence element can occur, allow for the occurrence of several degrees of emphatic prominence. / Department of English