The joint action of Unesco and UNEP in preparing this state-of-knowledge Report on tropical forest ecosystems can be seen as a natural outcome of the desire to provide better guidance to research that is vital for the satisfactory management of these ecosystems and to contribute to the training of specialists in the various scientific fields involved. Not only does this initiative follow logically from the priority accorded by Unesco and UNEP in their respective programmes to tropical forest ecosystems, it also provides another opportunity for Unesco to underline its preoccupation with the synthesis and diffusion of knowledge. For this reason the Report attempts to summarize the results of research undertaken over the past two decades, to point out gaps in knowledge and to sketch out the lines of future research. It is therefore intended as a tool for action while at the same time offering teachers and students a valuable source of information and documentation.