The deliberate release of genetically modified organisms (GMOs) implies the potential occurrence of environmental impacts which are either unexpected or only partially predictable and, thus, necessitates development of appropriate monitoring methodology. Therefore, new challenges have to be met when implementing the post market environmental monitoring (PMEM) of genetically modified organisms (GMOs), which is mandatory according to the European legal framework. According to Directive 2001/18/EC PMEM has to follow standard methodologies, wherever available and appropriate. To provide all involved parties with appropriate standard monitoring methods, the so called VDI Guidelines are developed by working groups established by the Association of German Engineers (VDI). These working groups are composed by external experts participating on a voluntary basis. The VDI is an independent technical standardisation body. All Guidelines are published in German and English and can therefore be used throughout Europe. VDI Guidelines are available in the field of exposure of the environment to GM plants (e.g. standardised sampling of pollen, standardised observation of hybrids or ferals), bio-molecular analyses (e.g. standardised extraction and detection of transgenes or their products in different environmental compartments), and the standardised monitoring of effects on non-target organisms (e.g. butterflies, wild bees, amphibians or soil organisms). The aim beyond this work is to facilitate generation of reliable and comparable monitoring data and enable an effective and efficient PMEM with high acceptability to the scientific community as well as the general public.