Following a request from the European Commission, the Panel on Genetically Modified Organisms of the European Food Safety Authority (EFSA GMO Panel) assessed the post-market environmental monitoring (PMEM) report for the 2013 growing season of maize MON 810 provided by Monsanto Europe S.A. The EFSA GMO Panel concludes that the data related to insect resistance monitoring does not indicate a significant and consistent decrease in susceptibility of the target pest field populations to Cry1Ab protein in Spain over the 2013 growing season. However, considering that the methodology for insect resistance monitoring remained unchanged compared to previous PMEM reports, the EFSA GMO Panel reiterates its previous recommendations for improvement of the insect resistance management plan of maize MON 810. The EFSA GMO Panel also recommends, as part of general surveillance, the continuation of the screening and discussion of literature on possible adverse effects of maize MON 810 on rove beetles. In the absence of information on the general surveillance of maize MON 810 in 2013, the EFSA GMO Panel cannot conclude on potential unanticipated adverse effects due to the cultivation of maize MON 810 in 2013, or on possible changes to the methodology as compared to previous growing seasons.