Since the end of the quasi-moratorium on genetically modified organisms (GMO) in the European Union in 2004, the establishment of GMO-free zones has become an EU wide phenomenon. In contrast to other European countries, Germany follows the concept of cooperative GMO-free zones where neighbouring farmers contractually refrain from GMO cultivation. In this article, we address the question which underlying factors could account for the establishment of cooperative GMO-free zones in Germany. Drawing on the existing literature on spatial agglomeration of different farming systems and the establishment of GMO-free zones, we provide the first systematic study on driving factors for the regional formation of GMO-free zones in Germany. The empirical analysis is based on a unique data set at the federal states level for the years 2004 to 2007. We show that infestation rates with the European Corn Borer, imminent Bt maize cultivation in the near vicinity and the number of arriving tourists mainly account for the establishment of cooperative GMO-free zones. This finding is consistent with the view that it is more the overall rejection of agro-biotechnology by broad strata of the population, including stakeholders in tourism and environmental protection, than economic benefits at the farm level which make German regions establish GMO-free zones.