A major objective of the European Commission Monitoring Working Group (MWG) on Guidance Notes supplementing Annex VII of Directive 2001/18/EC was to explore the possibility of European Union (EU)-wide coordination and harmonisation of data resulting from monitoring of genetically modified (GM) crops. Firstly, we present concepts for the coordination and harmonisation of monitoring data of cultivated GM crops. We argue that data coordination is necessary at both national and EU level and that data harmonisation is advisable at different technical levels of monitoring. Secondly, we explore the applicability of existing monitoring programmes and data infrastructure schemes run at EU level for monitoring of GM crops, and options for implementing data coordination and harmonisation. Our work identifies useful European monitoring programmes and data infrastructure schemes for the monitoring of GM crops. Their relevance, however, needs to be analysed in more depth.