This European Standard provides guidance concerning the procedures for setting up a valid sampling strategy to meet the objectives of a monitoring strategy for GMMs released into the environment. Since monitoring methods of microorganisms in environmental samples usually require pretreatment of the samples, for example the extraction and isolation of GMMs and/or their nucleic acid, this is included in scope of this European Standard. The sampling is to provide material to which subsequent analytical or biological methods for monitoring of GMMs can be applied.