There is an urgent need for guidelines for monitoring of genetically modified higher plants, GMHP. Biotech crops are now cultivated in large scale in North America and elsewhere. In Europe, new genetically modified (GM) products will probably be placed on the market soon and made available of any negative ef for cultivation in the field. Monitoring and surveillance programs for detection fects to the environment must be designed and ready when these crops are released. This also corre sponds to the current intentions made by the European Commission to include monitoring in current biotechnology regulation. Monitoring of changes in biological systems is different from other types of environmental monitoring, such as monitoring fate of chemical pollutants, by focusing primarily on organism survival and organism interactions instead of physical and chemical parameters. The difficulties involved in monitoring biological systems are great, due to the complex interactions between organisms and the variability in responses. Problems concerning spatial and temporal pa rameter variation increase the difficulties, but may be remedied somewhat by the use of "baselines". These and many other questions are discussed in the present book with the aim of presenting practi cal solutions to the needs of GMHP monitoring. A project was initiated in 1998 to produce a book with guidelines for monitoring and surveillance of GMHP. In two earlier books, compilations of current test methods for risk assessment of GMHP were presented (Kjellsson & Simonsen 1994, Kjellsson et al. 1997).