Biodiversity offsets are conservation activities intended to compensate for the residual, unavoidable harm to biodiversity caused by development projects. The goal of the report is to explore the potential and limitations of biodiversity offsets as a tool for conservation: to consider the concepts involved, such as "net benefit" and "no net loss", as well as why, where, when and by whom biodiversity offsets might be used, and what issues remain to be resolved. This report contains a synthesis and interpretation of a series of semi-structured interviews about biodiverity offsets, conducted by the authors with 37 individuals from around the world between March and August, 2004. The report also contains the results of the interviews and preliminary conclusions regarding the potential and limitations of biodiversity offsets, and what should be done to improve them.