The rapid degradation of tropical rain forests and their biodiversity urgently demands effective action, which requires scientific knowledge. In this document, the authors present and elaborate a procedure to identify the most pressing needs for information on tropical rain forest biodiversity. The priority-setting procedure starts with analysing the demand for information from people responsible for the conservation and wise use of tropical rain forests. Objectives of forest policy and management are identified, for which information on biodiversity is indispensable. Next, the authors propose specific actions and activities that are required to realise these objectives. Biodiversity information needed to execute these activities, is categorised in a matrix, according to the type of information (fundamental or site-specific) and its dimension (spatial, temporal or functional). The matrix shows the relevance of ongoing or proposed research, the information on biodiversity needed for actions to be taken, and desired improvements of research methods. The availability of information and methods determine whether research should be undertaken. Additional criteria are formulated for final priority setting, such as the sensitivity of policy actions to the information produced, the cost effectiveness of research proposals, the anticipated generic value and the degree of integration with related research projects. The document includes a procedure for seven of the most common and compelling policy and management objectives: - Land-use planning for conservation and sustainable use of forest land; - Designation and management of totally protected natural forest areas; - Protection and reintroduction of endangered species; - Support, adoption and documentation of indigenous management of tropical rain forests; - Use and valuation of non-timber forest products (NTFP); - Sustainable timber production and rehabilitation and productive use of secondary forests.