​This study uses a GIS spatial analysis at a global scale to provisionally delineate the areas that the Convention on Biological Diversity Programme of Work on Dry and Subhumid Lands, and hence also the Joint Work Programme, encompasses. Maps of the WWF terrestrial ecoregions (WWF-US 2004) and of aridity zones (CRU/UEA; UNEPGRID 1991) were used to identify areas included within the CBD definition. This study reveals the need for an agreed global map of dryland areas, highlights some issues in delineating dryland boundaries, and offers a provisional map for discussion.