The ZT Corpus (Basque Corpus of Science and Technology) is a tagged collection of specialised texts in Basque, which aims to be a major resource in research and development with respect to written technical Basque: terminology, syntax and style. It is composed of two parts, a 1.6 million-word balanced part, whose annotation has been revised by hand, and another automatically tagged 6 million-word part. We built new tools to help in building ZTC: corpus compilation, corpus annotation. and a specific interface for advanced queries. It was released in December 2006 and has been developed by Elhuyar and the Ixa NLP Research Group (On-line consultation: http://www.ZTcorpusa.eus). The ZT Corpus stands out among other Basque corpora for many reasons: it is the first specialised corpus in Basque, it has been designed to be a methodological and functional reference for new projects in the future (i.e. a national corpus for Basque), it is the first corpus in Basque annotated using a TEI-P4 compliant XML format, it is the first written corpus in Basque to be distributed by ELDA and it has a friendly and sophisticated query interface. The corpus has two kinds of annotation, a structural annotation and a stand-off linguistic annotation.