A framework for the design of general surveillance during commercial cultivation of genetically modified (GM) crops according to current EU legislation 2001/18/EC is presented. The framework is based on a previously established concept for environmental post-market monitoring (PMM), which identified clear conceptual differences between case-specific monitoring (CSM) and general surveillance. While CSM focuses on anticipated effects of a specific GM crop, general surveillance is designed to detect unanticipated effects on the environment. Two separate frameworks are proposed for developing either of the two programmes. Considering its focus, general surveillance has to be based both on the subjects of environmental concern (safeguard subjects) that should not be adversely affected by GM crop cultivation and on the environmental quality that should be preserved therein. Unanticipated effects in the defined safeguard subjects may be detectable by using existing monitoring networks and by establishing appropriate reporting systems. Results from general surveillance can, however, not be linked to any specific attribute of GM crop cultivation, and causality to environmental damages will have to be determined via specific risk assessement studies. The proposed structure for general surveillance represents a pragmatic approach to a realistic and feasible PMM programme and will be of assistance to industry, researchers, and regulators when assessing GM crops during commercialisation.