This is the first dictionary of Old Gascon organised on thematic principles. It covers the period from the earliest extant documents to the 17th century and extends to all relevant idioms and sources - Old Gascon texts, medieval Latin and regional French. The complete dictionary will comprise some 130 80-page fascicles. From Fascicle 12 onwards the DAG is being published with a new structure for the articles, which provides more scope for semantic description and phrases. Instead of giving a multiplicity of instances, in future one selected example will be provided for purposes of contextualisation, which will enhance readability.