Notifiers of genetically modified plants under Directive 2001/18/EC or Regulation (EC) 1829/2003 have to provide with their application a plan for general surveillance. The objective of this general surveillance is to identify the occurrence of adverse effects of a particular genetically modified organism (GMO) on human health or the environment which were not anticipated in the environmental risk assessment. These are most likely to occur where the exposure to the GMO is highest, i.e., in the farming environment where GMO cultivation takes place. EuropaBio considers that a well designed farmers' questionnaire is the most appropriate tool to meet the objectives of the general surveillance obligation. Other existing sources of information, such as surveillance networks, company stewardship programmes and relevant scientific publications, may be used where appropriate. The complexity and dynamics of the agricultural landscape need to be taken into account when analysing observed effects, since there are many potential causes for unexpected observations.