The aim of this work is the construction of a syntactically annotated treebank for Basque. In this paper we present first, the basis of the annotation. After examining several options we chose the scheme presented in (Carrol et al., 1998). It follows the EAGLES standards and it is based on the idea of adding to each sentence in the corpus a series of grammatical relations specifying the dependencies between modifiers and their nucleus. After the formalism has been presented, we will describe the problems we have found and the decisions we have taken to solve them. Next we present an example showing the application of the scheme to an initial corpus. Finally, we present the main conclusions about the applicability to Basque and future work.