The regulatory framework for growing GM crops in Germany comprises quite liberal ex-ante regulations with very strict ex-post liability rules to protect other production forms from possible negative side effects of transgenic plants. Regulation is assumed to impose additional costs on farmers who intend to plant Bt-maize. This paper investigates the significance of these costs and the possibility of minimizing them by farm-level strategies such as coordination and cooperation between the Bt-maize growing farmer and his neighbours. A case study investigating the behaviour of Bt-maize growing farmers was carried out in the Oderbruch region in the federal state of Brandenburg, Germany. This region is leading in Bt-maize cultivation in Germany and has a high incidence of the European Corn Borer (Ostrinia nubilalis Hübner). The interviews revealed that additional costs due to ex-ante regulation and ex-post liability were only of minor importance to the Bt-maize growing farmers. All farms were large-scale and could easily manage the construction of buffer zones within their own fields and deliberately avoided the planting of Bt-maize close to their neighbours. Thus advanced inter-farm coordination and cooperation was not necessary to achieve coexistence. However, the fact that Bt-maize was only grown on large-scale farms indicates a significant threshold effect due to the regulatory framework in Germany likely to prevent small-scale farms from planting Bt-maize unless innovative farm-level strategies of coexistence will be developed.