{Reference Type}: Journal Article {Title}: How can flexibility be integrated into coexistence regulations? A review. {Author}: Devos Y;Dillen K;Demont M; {Journal}: J Sci Food Agric {Volume}: 94 {Issue}: 3 {Year}: Feb 2014 {Factor}: 4.125 {DOI}: 10.1002/jsfa.6358 {Abstract}: Member states in the European Union (EU) implemented both ex ante coexistence regulations and ex post liability schemes to ensure that genetically modified (GM) and non-GM crops can be cultivated side by side without excluding any agricultural option. Although proportionate coexistence is best achieved if regulated in a flexible manner, most implemented coexistence regulations merely rely on rigid measures. Flexible coexistence regulations, however, would reduce the regulatory burden on certain agricultural options and avoid jeopardizing economic incentives for coexistence. Flexibility can be integrated at: (i) the regulatory level by relaxing the rigidity of coexistence measures in ex ante regulations, yet without offsetting incentives to implement coexistence measures; (ii) the farm level by recommending the use of pollen barriers instead of large and fixed isolation distances; and (iii) the national/regional level by allowing diversified coexistence measures, which are adapted to the heterogeneity of farming in the EU. Owing to difficulties of implementation, the adoption of flexible and proportionate coexistence regulations will inevitably entail challenges.