Modelling is the only way by which one can hope to become really predictive concerning the fate of GMOs in agricultural ecosystems. Unfortunately, in this area, very few efforts have been developed. This paper presents some models of gene and plant dispersal taking into account diverse factors ranging from pollen dispersal to agricultural practices. These models could, once validated, allow to predict the environmental impacts of the cultivation of GMOs. Only once a real effort has been devoted to such studies, including experimental parameters determination and validation can we hope to make reliable predictions on this topic.