In March 2001, the European Parliament passed the Directive 2001/18/EU (concerning the deliberate release of genetically modified organisms), which demands that genetically modified organisms are monitored after placing them on the market as, or in a product. The purpose is to protect the human health and the environment from possible harm coming from these organisms. Since then there is an active discussion of scientific, organisational and legal questions regarding the installation in national laws. Among others the working party, Anbaubegleitendes Monitoring gentechnisch veränderter Pflanzen im Agrarökosystem guided by the Federal Biological Research Centre for Agriculture and Forestry serves as a forum attended by several public and private institutions. The authors are members of this group. In this paper suggestions about the design of a monitoring regime are presented, focussing on genetically modified plants in agroecosystems.