This paper discusses the contribution of biomass in the future global energy supply. The discussion is based on a review of 17 earlier studies on the subject.. These studies have arrived at widely different conclusions about the possible contribution of biomass in the future global energy supply (e.g., from below 100 EJ yr(-1) to above 400 EJ yr(-1) in 2050). The major reason for the differences is that the two most crucial parameters-land availability and yield levels in energy crop production-are very uncertain, and subject to widely different opinions (e.g., the assessed-2050 plantation. supply ranges from below 50 EJ yr(-1) to almost 240 EJ yr(-1)). However, also the expectations about future availability of forest wood and-of residues from agriculture and forestry vary substantially among the studies.The question how an expanding bioenergy sector would interact with other land uses, such as food production, biodiversity soil and nature conservation, and carbon sequestration has been insufficiently analyzed in the studies. It is therefore difficult to establish to what extent bioenergy is an attractive option for climate change mitigation in the energy sector. A refined modeling of interactions between different uses and bioenergy, food and materials production-i.e., of competition for resources, and of synergies between different uses-would facilitate an improved understanding of the prospects for large-scale bioenergy and of future land-use and biomass management in general (C) 2003 Elsevier Science Ltd., All rights reserved.