A contribution to the WRI/IUCN/UNEP Global Biodiversity Strategy. Includes bibliographic references. This paper sets out a framework for assessing conditions and trends in biodiversity at local, national, regional and global levels. The paper reviews the role that indicators play and outlines what needs to be measured. A set of 22 indicators is presented, organized in 3 categories: indicators used to measure wild species, indicators used to measure diversity and indicators used to assess domesticated species (crops and livestock).