Abstract: The ground beetle fauna was studied at two experimental field sites in Poland. The aimof this study was to determine the long term impact of Bt maize on non-target organisms incomparison to conventional maize. For this purpose, Bt maize (DKC 3421 YG) expressing theCry1Ab toxin and the respective isogenic non-Bt variety (DKC 3420) were cultivated underidentical conditions. For comparison, two non-Bt cultivars sprayed with a lambda-cyhalotrinewere also included. Population density of surface-active invertebrates was monitored using pitfalltraps (4 per plot). In the first year of the study, no significant differences between Bt maize andthe conventional treatments were detected.