Abstract: The present study is a part of the project focused on the environmental impact of GMmaize MON 88017. Our aim was to assess the occurrence, abundance and distribution ofentomopathogenic nematodes and their insect hosts in the experimental field with MON 88017GM maize and non GM cultivars. Steinernema affine was present in all maize cultivars and themost important factor affecting it’s occurrence was probably the type of the neighbouringenvironment, as EPNs were only present in plots in the part of the field neighbouring with aforest, regardless of the maize cultivar. No effect of MON 88017 on EPN distribution wasrecorded. The overall EPN density was low, probably reflecting the low number of soil insects.Thus the biocontrol potential of such a population would be limited.