Recent advances in the use of permanent plots for monitorin forest biodiversity in the Old World. The theoretical framework behind plot-based monitoring and a description of how plot-based results have been put to a variety of uses, such as defining the number of trees to be sampled in smaller plots, monitoring climatic change, ground-truthing satellite imagery to map paterns and developing new analytical techniques for assessing patterns of diversity. A final section outlines some of the monitoring programmes and networks currently in place in Europe.