This paper describes the current method of general surveillance of genetically modified plants (GMO) in the European Union that is aimed at the detection of unexpected adverse effects of the GMO (those that were not identified in the environmental risk assessment) at the farm level. The weakness of the current method in detecting the ecological effects of GMO due to a lack of a well-defined control (usual scenario in the absence of a GMO) is described, and a more quantitative method of assessment (that which involves the collection of data on both GM and non-GM crops) is proposed.