The FAO requested the Institut français de Pondichéry to organize a one-month training course on the "Assessment of biological diversity of forest ecosystems". This training course was part of a French funded project implemented by the FAO in Cambodia, Laos and Vietnam with the aim to "Establishment/strengthening of country capacity in planning, assessment and systematic observations of forest resources in South-East Asian countries" (GCP/RAS/157/FRA). While dealing with biological diversity, the distinction is often made between the different types of diversity. These types refer to spatial scales and levels of organisation. For this training course, the focus was on the species diversity at different scales (within communities, ecosystems, landscapes and regions) and the community and ecosystem diversity (within landscapes and regions) rather than on genetic. The task was thus to try to bring together the classical perspective of forest inventories and the ecological approach which is more often followed by researchers. We thus had lectures on the definition of biological diversity itself, on the biological and ecological evolutionary processes which help creating or maintaining diversity, on vegetation and forest mapping and the way to include ecofloristic information, on sampling strategies and on the utility of permanent plots. We also thought that it was necessary to mention the role of human societies, not only by considering the level of migration due to human activities but also by providing an insight into how minor forest products can be quantified and valued. Indeed, timber and non timber forest products constitute a direct link between the existing biological diversity, the needs and activities of the local population and the social and economic value attached to the maintenance of species and ecosystems.